The Yugo SKS is quite reliable, as long as it's in original condition. The one thing to watch for is to make sure the firing pin is not sticking in the bolt (due to built-up preservative grease, for example). A thorough cleaning will make sure that it's free enough to rattle when you shake the bolt.
As for accuracy, it's a medium-accurate rifle for short to medium range. Out to about 150 yards it should be accurate enough to do it's job, but it won't put all the bullets into the same hole even at closer ranges.
It shoots 7.62x39mm ammo, which is about the cheapest rifle ammunition available. You can find the ammo both new or surplus, often for about $.10/round. The magazine is hinged at the front, so it can swing open to empty, but it isn't designed to be removed from the rifle unless you're field-stripping it for cleaning. Some aftermarket, larger magazines are available. They're not recommended - they were designed for other SKS versions, not the Yugo, and don't feed reliably. Also, modifying the Yugo SKS to take them is illegal unless a lot of other changes are made (strange federal law involved here - search other threads for more details).
It's a fun rifle, and inexpensive. Get one!