Originally Posted by Eatadonut
...seems silly, needlessly complicated, and possibly dangerous to your new RD (because if you can't trust yourself to properly break a chain, is partially disassembling a RD a good idea?)
Removing the idler pully from a rear derailleur is about as simple a procedure as there is. Remove one bolt, slip out the pulley, install the derailleur, reassemble in reverse order. Bike mechanical jobs don't come much more straightforward.