Definitely. If all you plan to do is surf and use Office apps you'll be fine. No heavy processing required. And do you mean a motherboard which is backwards compatible with AM3/AM2?
yeah, is an am3+ motherboard backward compatible with an am3 cpu? and are the heat sink mounting options the same?
Well there's more than one answer to your question. Not all AM3+ motherboards are backwards compatible with socket AM3 cpu's. It depends on the manufacturer's specs. The same goes for the heatsink. All the details about compatibility are listed in it's specs.