How hard would it be to swap out the fixed card ADF's in the standard MS2002 Aircraft and put in an RMI instead?

Two ways: Harder and Easier!The harder way is to open the panel.cfg file, find the old gauge, and replace it with the new gauge. You may find it easier to comment out the old gauge with a "; or //" in front of the gauge, then insert a new line above or below this commented line (actually you could copy the commented line and just replace the name of the gauge).The easier way is to use CfgEdit (freeware) or FS Panel Studio (shareware) from www.cfgedit.com . They will indicate CfgEdit is not compatible with FS2002, which is partly true since it will not open the new style XML gauges contain in the fs2002gauges*.cab files.