I have a shimano xtr rd-m952 rear derailleur, and need to fix the jockey wheels. They are about $30 each. There are new derailleurs to be had on ebay for about $80 or so. I am wondering which ones are compatible with my setup.

2000 stumpjumper fsr comp
xtr front and rear derailleurs
xtr cranks


The other option is to fully rebuild this one, maybe with a new spring etc. How difficult is it to replace the spring?