Safdar bhai, i am still a noob with CM when it comes to devices other than S3, S3 mini and S4.
However, CM is easy. They provide all the details. First you have to read
Why Mod? - CyanogenMod
and realize your requirement.
To ease the mystery, bloatware is part of the Stock rom that OEM provides in the phone. e.g. Samsung sets have samsung services (push service, update service, app downloader service etc etc) running in background. These cannot be removed or isolated unless the phone is rooted. Even then, stopiing some services will affect operation of other critical functions and thus your phone would behave randomly. So the best idea considered is to replace a Pure Android Rom.
Atleast, thats what I understood back then 
Next: Go through Information: Samsung Galaxy S II (T-Mobile) ("hercules") - CyanogenMod
or more specifically How to Install CyanogenMod on the Samsung Galaxy S II (T-Mobile) ("hercules") - CyanogenMod
You'd have a clear idea by now what and how to do. Once you do CM, in future you can try other roms as well.
For your second question, almost everyone is skilled in PK when it comes to mobile repairing. I have absolutely zero clue on who works best with mobile repairs. Both Hafeez Centre and Hall Road have the repairing minds.
