My local Big 5 will advertise either the 91/30, M38, and M44 on sale for $79.95 about twice a month. I just picked up a 91/30 that is an Izhevsk Arsenal from 1931 with all-matching serial numbers. After a week of cleaning, I can get 4" groups at 200 yards using old Russian milsurp 205gr ammo. Corrosive but a hosing off of the barrel and bolt face with Windex with Ammonia kills the salts and then just clean normally.
There is a tremendous amount of information on Mosin-Nagants on a number of forums:
http://www.russian-mosin-nagant.com/phpBB2/index.php
http://www.surplusrifle.com/russiannagant/maintenance.asp
http://www.websitetoolbox.com/tool/mb/surplusrifle
Another site is
www.mosin-nagant.net but it appears to have been suspended by the web hosting company for now
There was a lot of good information there, hope it comes back.
You might want to print this page when you go to look at any of the Mosins:
http://www.russian-mosin-nagant.com/Arsenals.htm This will give you a basic idea of where the rifle came from. Take a bore light or a tiny flashlight to inspect the bore, looking for rust or pitting or counterboring.
There will be a lot of funny-looking cyrillic characters punched around the receiver but the majority of those are proof marks or from re-arsenal work. For example a square box with a diagonal line in it is a re-arsenal mark (may also appear on the stock). Lots of cosmoline on most of them so a good cleaning will usually produce a very nice looking rifle.
The Mosins have s/n's on the receiver, bolt, and bottom of the mag well. Try to find a rifle with matching numbers. The M44 is a real fire breather. It will kick like a mule and depending on the ammo, will provide lots of muzzle flash.