new rail extension finally arrived... question?

My 'gift pack' from FNH finally arrived! I got the MI Rail Extension and four more mags. SWEET! So... heading out tomorrow for some deer hunting and I just sighting in my irons and my scope. In order to install the rail extension, I need to essentially remove the barrel, assemble the extension, and put it all back together. So my question (and I'm pretty sure I already know the answer...) is - will my sights and scope require re-zeroing after re-installing the barrel? I don't really have time to get the range again before I head out and our deer camp has a rule that there is no shooting before opening morning...

Not a big deal if I have to wait but it would have been awesome to have it put together before hunting. I have a GG&G XDS-2 bipod that mounts on the bottom rail and to leave room, my foregrip is slid back farther than I'd like... I may just not use the bipod for now...