I've done several, and they're a real PITA. Worst part is the steel " plug" that sets opposite of the loading tap. It keeps the pellet from dropping in too far. It has to come out to remove the valve, and it's a bugger to get out. Even worse to put back in. If I remember right, half the valve comes out the back, and half goes out the front. I do remember a LOT of cussing was involved with every one I did.
I've worked on a couple of the 700's before. I don't remember having a bad time with that bushing plug but then my ex was happy to give birth to three kids. There was lots of cussing with each of them. Here's a link that may help. Navigate a bit and he walks you through the reassembly as well. Good luck.http://anotherairgunblog.blogspot.com/2008/12/disassembling-crosman-707-rifle.html