firmware

I recently attempted to get a firmware update on a old Garmin GPS150 TSO. (I see other POA members discussing similar issues) The avionics shop near me couldn't help, suggested I call Garmin. The tech at Garmin (nice fella - spent 45 minutes on the phone with me) confirmed what I alerady knew...

I used to fly with a GPS155XL IFR certified Non-WASS GPS. It did not have a pretty color display but worked great for me. I’m considering installing one in my old 172, but want to know if anyone out there has any recent experience with one of the legacy Garmin GPSs. If so, what Firmware...