Welcome, Frazod and other fellow Mosin fans. I started with one $69 rifle, and somehow wound up w/4 or 5 of these Mosin-Nagents before I made myself stop. Here's a good info source:
http://7.62x54r.net/
If you have a chance to look 'em over when you buy, I look for ones that have been treated with 'pine tar' - they don't have the orange-shellac shine that most of the guns have, they're a 'softer' mottled finish. While not a hard & fast rule, it usually indicates the gun was captured by the Finns during their Winter War with Russia, as the Finns used this stuff on most of their guns. Look for a 'proof mark' of the letters SA in a small box, on mine they're just ahead of the receiver, right side. The SA indicates it was processed by the Finnish army - they captured a ton of them at the start of their war w/Russia, more as the war went on, then bought a bunch from Germany (who also captured a lot of Russian rifles, but had no real use for 'em). Keep your eye peeled for Mosin's marked as made by Remington. They built a few boatloads for the Czar, who went under before we made delivery. The US armed some insurgents to fight the commies (the White army) w/these guns. Some of these would have interesting story if they could talk.
The Finn's sometimes just handed these out 'as is' after they marked them, sometimes they refurbed the rifles, sometimes they stripped them down and put new stocks on (w/finger joints in the stock that let the guns stay accurate in sub-zero cold -these will have pine tar, as a rule).
Some of them they eventually rebuilt into different guns using the original receiver. There were some intermediary models, but the ones I see are M39's, they'll be $250 - $400 and I like 'em. Many of these were rebuilt from scratch on an old receiver. You can get a looksee here, this fellow sells them 'online' (note that the ones w/receivers older than 1898 (or 96, look it up if you care) are deemed 'antiques' and can be shipped to your door instead of to a dealer. Saves you a transfer fee, $20 here but higher elsewhere)
http://www.gunsnammo.com/
The Russians have boatsloads of these, still, and they arsenal-refinish theirs before export, so your $90 rifle will generally be in good shape - look good, work well. Expect 'frosted' bores (they've always used Berdan style primers) so if the bore isn't shiny - them's the breaks.)
I bought a lot of ammo a few years ago when it was REALLY cheap, I'd suggest seeing what your gun likes - there are 150 grain, 180, etc...the Czech silvertip I like, the Yugo stuff I like. New Tula or Wolf is dandy - if your gun likes it.
Expect to never figure out how the safety works on these things. As some Russian officer said when asked "Is gun. Is not safe!"