Is the amount that is owed what was shown on the return you filed? Or did the IRS do an audit or other adjustment resulting in the tax now owed. And is this an income tax liability (Form 1040) or some other kind of tax?
If this is income tax and the amount owed is what is shown on the return then the tax generally is subject to discharge if the bankruptcy petition is filed more than three years after the return was filed, which would be the case here. Fraud, of course, is one of the big exceptions to discharge, but that would have required that you had provided false information to the IRS. If this is income tax, though, it does not seem likely that what your lawyer has in mind is an IRS challenge seeking to exclude the tax liability from discharge. You said that the lawyer plans to sue the IRS; that suggests the lawyer plans to initiate an adversary action rather than responding to a motion filed by the IRS. (An adversary action is essentially a lawsuit filed within the bankruptcy action and is heard by the bankruptcy court.)
The phrase "insure against future collection efforts" could cover several different possibilities, depending on the facts of the liability, the assets you have, and the details of the bankruptcy proceeding.
One of the things that most people filing bankruptcy do not know is that while the discharge order removes the personal liability of the debtor for the debts that are discharged it does not result in vacating any liens that arose against the debtor prior to filing the bankruptcy petition. The IRS has an automatic lien on all assets and rights to assets of the taxpayer that arises from the date of the assessment of the tax. The IRS may perfect this lien by filing a notice of the lien in the office specified in state law for such filings. For most states, that office is generally the same place that judgments would be recorded. Absent some order of the court, that lien will still attach to any pre-petition assets of the taxpayer that the taxpayer still has once the bankruptcy is concluded. So, for example, if your home is exempt in the bankruptcy and the federal tax lien (FTL) attached to the home prior to the bankruptcy filing, then that lien would still remain attached to the home after the discharge is entered and the automatic stay is lifted. In that case the IRS could collect the tax from the home either by seizing and selling it (which is not real common, but can be done) or by simply collecting from the proceeds of sale when the house is sold.
So one possiblity here is that the lawyer has in mind trying to strip the lien off of exempt assets that you had at the time the petition was filed to avoid the IRS collecting from those assets once the automatic stay is lifted.
Another possibility is that the lawyer expects that there will be enough money in the bankruptcy to pay the actual tax and interest owed, but wants to challenge the penalties to get them abated to avoid the IRS collecting for those penalties from those pre-petition assets.
There could be other possibilities, too. You'd need to ask your lawyer precisely what she has in mind here. You want to know that before you plunk down money to start this. I can tell you that $1,500 won't last long in an adversary proceeding, so there would need to be a significant benefit here to justify doing it. If you want some feedback after your lawyer says what the particular claim would be, you can ask that here and I might be able to provide some helpful comments for you. Note, too, that depending on what the lawyer has in mind, you might need a tax lawyer to do the actual adversary proceeding. Most bankruptcy lawyers do not have a real deep knowledge of tax law after all. You say the liability is just one year. How much is actually owed?
Well, I'm not one that is very knowledgeable on what the rules are for what is kosher.But certainly there are legitimate adversary actions against the IRS that can be taken in bankruptcy. Whether what you lawyer wants to do is actually something that might succeed is something I cannot tell you without the details of what she has in mind and the details of your situation. The IRS is involved in litigation all the time — as I recall the IRS has the largest number of lawyers of any federal civilian agency other than the Department of Justice — and there is a special court devoted to just hearing income, estate, and gift tax cases, the U.S. Tax Court, which gives you a pretty good idea of just how much tax litigation there is. (Which is good for my practice.) The IRS is a huge organization and one adversary hearing in a bankruptcy isn't something that will create some kind of grudge against you by the IRS later on. If you have a reasonable shot at succeeding with the action your lawyer has in mind and the benefit will justify the cost to do it then go for it. You don't need to worry about somehow angering the IRS.

But certainly there are legitimate adversary actions against the IRS that can be taken in bankruptcy. Whether what you lawyer wants to do is actually something that might succeed is something I cannot tell you without the details of what she has in mind and the details of your situation. The IRS is involved in litigation all the time — as I recall the IRS has the largest number of lawyers of any federal civilian agency other than the Department of Justice — and there is a special court devoted to just hearing income, estate, and gift tax cases, the U.S. Tax Court, which gives you a pretty good idea of just how much tax litigation there is. (Which is good for my practice.) The IRS is a huge organization and one adversary hearing in a bankruptcy isn't something that will create some kind of grudge against you by the IRS later on. If you have a reasonable shot at succeeding with the action your lawyer has in mind and the benefit will justify the cost to do it then go for it. You don't need to worry about somehow angering the IRS.