Several years ago, while shooting my Romanian SKS, the rear sight flew off and the spring underneath went awol.  Recently I pulled the SKS out of storage and have decided to add a Tech Sight.  I think I need to replace the rear sight spring even though I won't be using the original sight because it looks like the spring also serves to keep debris out of the top of the sight base.  As it is now, I can see the spring through the hole where the rear sight was, and I am afraid debris getting in there could cause a malfunction.

My question is, is there anything else that is supposed to go in the rear sight base besides the spring?  I think the Tech sight comes with a pin to retain the spring.  Anything else I  need to get this back into shape?