We have an old bike laying around, and my brother came up with the idea of "Fixing" it.

From what I can gather, I can leave the front wheel and both brakes alone, and just need to work on the rear wheel and other componentry. Since it needs a new rear wheel anyway (cracks and gaps right through the rim) what sort should I get? It isn't a flash or expensive bike, and it's steel and weighs a bit so weight isnt an issue, so doesn't really matter what type of wheel we get.

Also it has Shimano 105 Components, what bits can I keep and what do I need to change.

Anything else I need to consider?

BTW it is a 1992 Avanti Ultra, with Steel Frame.

Thanks.