Happened upon some old Munchkin cards. Can these be played together?

[Zero5360]

A few weeks ago, a friend introduced Munchkin to my wife and I at our weekly game night. We liked it so much that I bought the core set, printed May 2012. Just this last weekend, I was at a friend's house and I brought it up and he said his old roommate left his Munchkin cards at his place when he moved out years ago and offered them to me. Problem is, these look fairly old and the FAQ says that some of the older sets aren't compatible with the newer ones. Furthermore, there are expansions that I don't have the rulebook for.

Here are the cards I received. The only box is for the Demented Dungeons expansion and it is 1st edition, 1st printing, March 2008. I can only assume the other cards are older as Demented Dungeons is practically unplayed and the others are well-worn.

http://i.imgur.com/K7cp0rk.jpg

I couldn't find any dates on the cards, so here are some pictures. The far left card is from the set I just purchased and the others are from the stack I was given. There are some color variations that have me suspicious. Also, are the symbols at the bottom of the three on the right representative of the expansion they came from? If so, is there a list available so I might know which expansions I have?

http://i.imgur.com/EGUt16k.jpg

Lastly, is there any way I can buy replacement cards? There are about 40 cards that I found that are water-damaged and/or torn that I would like to replace.

Thanks for any information!