Mountain Biking - total newb... can anyone help identify bike?

Ok.. so I just bought a couple bikes for my wife and I cuz she has decided she wants to exercise and doesn't like jogging five to seven miles a day with me. So I went out and bought a Marin Alpine Trail and it definitely needs a new chain but don't even know where to begin. Other than that the bike only says edge x and 7005 on it and am understanding that only deals with the frame. I know it has a nice 3 piece crank and presume 9 gears. Just trying to find more info on bike and some pointers for setting it up for mud and dirt trails. Any help would be much appreciated as the net hasn't helped any. Lol.

What I was after is a year or perhaps a way to look up the bike and find out more than just 29er stuff. The chain is rusted through and needs the gears removed and oiled well cuz previous owner didn't ride, just left on apt patio. Just trying to find out all I can before dismantling and re-build. Any advice or cautions would be appreciated. Thx...

Go to Bikepedia.com and search under the "Bikes" section of that site. Your picture is sort of dark so it's hard to see any distinguishing decals.
As for the chain, you'll need a chain breaker, removal tool that you can buy at your bike shop along with a new chain. Determine the length of the replacement chain by using the old chain as your template. Do not try to ride the bike with that rusted chain, you'll ruin the cassette. I wouldn't disassemble the bike until I replaced the chain and see how it rides. But that's your call.

Looks to be 2007 vintage.

http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?Year=2007&Brand=Marin&Model=Alpine%20Trail&Type=bike

Thx... looks to be a 07 model. Oh and thx for the link and all the info on the chain, will take your advice on the chain as well. You've been a huge help... :)