I have a 1937 M91/30 that was in really rough shape when it came to me. No front sight, warped wood on the upper leaf of the stock, laminate peeling from the wood, and surface rust on the barrel.
The first part of this project was getting it operational. I dismantled the rifle completely, stripped the bolt apart, polished the trigger, lightly sanded the stock, cleaned off the globs of cosmoline from everything, and put it back together with a new front sight and some TLC. It cleaned up nice.
Part 1: I took it to the range and ran some commie surplus 7.62x54r through it until my shoulder was sore... about 80 rounds worth. ouch. It was awesome! Loud, accurate at 100 yards, and no issues to speak of... except for the shoulder breaking metal butt plate, which I replaced with a cheapie rubber pad for now. I threw some windex down the barrel to neutralize the corrosive salts and called it a day after cleaning the gun up with some Hoppes #9.
Part 2: Adding a bent bolt. This was easy. I used Rock Solid Industry's bent bolt body. I paid more for the bolt than I did for the rifle... but it looks and works excellently. I inlet the busted stock a bit with a round file to accommodate the bolt.
Part 3: I installed a scope mount. Some of you may be familiar with the JMeck scope mount. For those that are not familiar, it's an excellent accessory for your Mosin if you want a no-fuss, no-muss quick & easy scope mount that even I couldn't bugger during installation. Again, I paid more for this part than I did for the rifle itself... but this was incredibly worth it.
Part 4: I mounted a cheap 10-40x50mm Barska scope that I don't mind abusing with the recoil of the 7.62x54R. It took me 3 shots to walk it onto target... and then I was able to put shots #4-9 of cheap commie surplus ammo through the same ragged hole at 100 yards. You can cover the group with a Nickel.

Total cost invested so far:
-$80 for the beater rifle
-$80 for the bent bolt after shipping
-$80 for the scope mount after shipping
-$50 for the 10-40x50 Barska scope
-$15 for scope rings
-$10 for a rubber butt pad
$325 total so far.
Final pieces:
-Timney trigger? The stock trigger is awful, even with the stoning & polishing I gave it.
-BG-Tactical gun stock and bedding pillars. The original stock on mine is jacked up badly, and a high cheekpiece would be great for improved accuracy & ergonomics. The bedding pillars should make modest improvement in accuracy beyond 150 yards.
-Bipod for shooting at the range, sling for shooting in the field.
I know there are purists who think I'm the scum of the earth for doing this to a classic rifle, but the fact is that this gun came to me in terrible shape, and it will soon be a very solidly put together labor of love that will be kept in my family and slinging lead for a long, long time. Also, it will be ultimately cheaper than a Remington 700 in .308 or .30-06 with similar features, and it'll cost 1/5th as much to shoot until the commie surplus ammo dries up.