I have a Yugo 55 SKS. Not the Yugo 55/66 with the grenade launcher that you see commonly. I love it. Nice little gun.
As for the "Made in China" it is not like the junk you see "Made in China" on store shelves today. The SKS is a solid rifle design and there are many available. Most are probably aged from the early 50's to the late 60's.
Like evaluating any rifle, check the action, cleanliness, rifling in the barrel, wear marks, etc. You should be able to tell fairly easily if it's worth the asking price. I'm a little out of touch with the gun prices for the last couple years as my funds have been directed towards Jeep parts instead. Two years ago you could pick up SKS rifles anywhere from $75 to $300, but I think it's a little higher now.
Oh, if someone tells you they are selling an unfired SKS, I'd call B.S. on them. Most were used and the rearsenaled to be within spec., such as having new stocks or barrels added. Also I'd personally stay away from any SKS that has aftermarket stock added or has been converted to feed with a magazine instead of stripper clips.