how to remap keyboard keys?

[newdeal]

So I just bought a macbook pro off ebay and it turns out it has a french keyboard. As I am not french and am used to the regular keyboard I find this slightly irritating. Most things are the same but the punctuation keys are different and the return key is very tiny as they had to make room for some special keys. What can I do to reprogram the mapping of these keys? Most annoying is I would like the à key to be return because I keep hitting it since the return key normally would be big enough it would take the place of this key