The Volquartsen Target Hammer is your best bang for the buck. With just the hammer replaced ( kept the factory springs in ) it drop my trigger pull down to 3lbs. I tried the auto bolt release, but didn't like it, so I put the factory one back in. It was easier to release, but made it harder to lock open.
The hardest thing I tackled was reinstalling the bolt. I bought a tool for it made buy gunsmither that makes that job easier, it's not a must have item, for $16.00 it was worth it to me. It will also make installing your extractor easier.
If you go with a scope latter I really like the Talley light weight mounting system. I got the low set and they are perfect for a 33mm obj. scope.