In term of filing,
Quote Quoting Note on Where to File:
If filing for adjustment of status at a Service Center, you should submit the completed Form I-693, sealed in an envelope from the physician, with Form I-485 package to the Service Center. If filing for adjustment of status at a local office, you should submit the completed Form I-693, sealed in an envelope from the physician, at the time of your adjustment of status interview. Please note: some local offices request that you file Form I-693 with your adjustment of status application packet to allow for quicker processing. Please check the web page of your local office under "Local Filing Procedures" to determine if your local office wants Form I-693 at the time of filing Form I-485 or at the time of interview.
Ask the cost when you call the USCIS civil surgeon(s) you are considering using. I would expect the cost to be under $200.