How do I replace my rear wheel?
It should be easy to replace your wheel. The wheel is a 26" (this is a standard mountain bike size wheel), and you will also need to match it to the right cassette. from looking at your bike, its likely a 7 or 8 speed cassette. Your local bike shop should be able to tell what size cassette you need based on your rear deraileur, which wasn't stolen. With wheel, tire and cassette you are probably looking at a $100+ repair if you buy it all new. If there is a local bike co-op in your area that can help you with used parts and labor then you can probably do this for $30-50.