Nagant- very simple... sometime the barrel bands can be a b****, try to do as little prying as possible so you don't booger up the wood.
SVT- watch for flying springs... that are a few pieces that are under a little pressure and have been known to fly across the garage...
I know you probably already know this but as with all guns, use the right size screw driver so you don't strip any screws.
Congrats on the SVT.... I'm jealous!