I want to replace the main spring housing first to get rid of the crappy ILS one.  What all do I need besides the housing?  I've heard the ILS uses different pins and such than a standard housing.

Also I plan to take it to a smith for a trigger job.  Will an officer size frame use all the same trigger internal parts or are they any different in size from a government 1911?  I've never had a compact 1911 before and haven't stripped it down all the way so I'm not sure.

Stuff you will need to switch out that ILS:

-a new mainspring housing, obviously
-a new mainspring, Officer's ACP length
-a new mainspring cap, mainspring housing retainer pin (both in Officer's ACP size, which is larger in diameter)
-a new mainspring cap pin

The fire control parts for a trigger job, such as the hammer, disconnector, and sear, sear spring, and trigger are all the same as any other 1911, with the exception of a Colt Gold Cup.