I haven't replaced a compressor, but did replace lines on my wife's car recently. I believe the only difference is that you must make sure the compressor has X amount of oil in it, and never set it in a position other than the way it mounts (to keep the oil where it is supposed to be).
Evacuating the system and adding freon is not bad at all with the proper tools. Around here AutoZone has a loan-a-tool deal where you basically buy the tool, use it, and take it back for a full refund.
You need a vacuum pump capable of pulling 29" of vacuum and a manifold gauge set. At AutoZone, it was $200 for the pump and $100 for the gauge set. So, without the loaner / refund deal - it wouldn't be worth doing yourself.
I pulled vacuum 3 or 4 times just to make sure there were no leaks and all the moisture was gone. Wait 15-20 mins each time to make sure the pressure holds steady.
The gauge set had instructions on it, which you should be able to find online. The brand was MasterCool. I can't seem to find them right now
I recommend getting an extra freon can tap so you can bleed the fill hose prior to charging the system. The set comes with one, but when you unhook the fill line from the vacuum pump, air will get in the line - and you don't want that getting into your system.
CURRENT - ordered 10/26, home 1/142008 JK Unlimited,3.8L,6-spd,limited slip,dual tops,tow pkg,all power
SOLD1999 XJ 4.0L,AX15,NP231,D30HP,C8.25
STOLEN1993 XJ 4.0L,AW4 ,NP231,D30HP,C8.25:::C4X4 THB:GDI 3row:K&N:JKS QD: Dynomax#17340:MagnaflowCat#23221:Surco 45x60