go the the hardware store and get "easy outs" and a drill sized to work with the correct easy out.
drill the hole and insert easy out and back the bolt out.
sounds easy.. but can be a pita. sometimes you will need to re-thread the hole
You if you got the new chain and sprockets as well as the lower chain guide.. you could go with out the front guide. just make sure your chain is not worn beyond service limits and you keep the chain at the correct tension.
here's a nice little link to using an easy out
http://www.crustyquinns.com/tech/easyout.html