I have a M&P15 ORC, and i bought a handguard to replace it.

Problem is, it was bigger than the 6 3/4" handguard the rifle came with.

I had it returned and bought a smallerone to solve the problem, but a question still lingers...

Eventually when i want to put a handguard that is lager than the standard handguard, do i have to modify the gas system and that piece in front or can it be moved?

http://c4.ac-images.myspacecdn.com/images02/35/l_0d8ff9682a3341a9833d69b81b11d3f7.jpg
^This thing at the end of the handguard
I see a pin which looks like it can be punched out but im very new to this so i ask alot of questions.

Does that have tobe gunsmithed?

the problem i see is moving your gas block. the hole is drilled in the barrel for your gas system. So moving it isnt going to work unless you change your barrel to a midlength or something

You dont have to modify the gas system.  What you need to do is replace the gas block with a low profile one and replace the handguards with a free float system that covers the gas block.

Is it possible to go the opposite direction?  From the 9" hand guard to the 7" without having the gas tube/front sight look odd way out in front of the guard?

Ummmm, short answer, NO.

+1