Tune vs new PCM?

[aziff]

This gets thrown around a ton, thus making it hard to search for what I want to know, but would replacing my PCM with say one from ZZP skip me from having to get a tune or would I still end up having to tune the new PCM anyway?

Forgive my ignorance, but in either case where would one get a tune? GM dealership? Do they dial things in specific to your mods and stuff? What is the purpose (what do they change)? Andddd, what does it usually cost?

Thanks!

[TheOtherNick]

No a dealer cant do it,
zzp pcms are not recomended
A in car tune would be the best, but if you just are doing basic mods a dhp pcm from 3800 performance is your best bet, unless you can get a hold of overkill performance since your up north.

[aziff]

so basically, a new PCM from 3800 performance like this one is already tuned up to accomodate the basic mods done to my car and would just optimize the engines operation... (tune in a box)?