I have heard you can upgrade your weapons with added scopes and other parts. Anyone know more about this? Can you do it with all the weapons?

http://fallout.wikia.com/wiki/Fallout:_New_Vegas

Read up.

Yep- you can. I'm not sure of the system, but it seems to be something they had in FO2 and brought over.

Though there are going to be common-sense limits... "Whaaat? Why'd you put a scope on your Minigun? You can't fire it from the shoulder!" Though I'm sure the minigun gets some kind of upgrades as well...

I wonder if we'll be able to construct custom using schematics via F3. I've seen the Shiskabob in a vid once, but hope that weapons like the Rock-It Launcher and Dart Gun will return as well. Hell, even some new toys that do crazy things (which, I think, has been stated.. maybe).

Alright so 3 upgrades max per gun. I wonder if they use standard parts (like a scope), or an extra-zoom scope and stuff.

http://fallout.wikia.com/wiki/Weapon_mods

This tells you some of the mods and how they effect different aspects of gameplay