don't get the 4040 from smarthome it is way too expensive. Try the IR543 from homeautomationnet (good price, advertises on this site and he is in here helping people on his spare time).

Also if you have a lot of X10 stuff on different house codes, then the 4040 or the IR543 (same device) are not enough. You will need the modified IR543AH, it can send any house code, so you can send to all 256 addresses instead of just 16.

No you cannot use the Prontos RF except if you are in Europe and have a Pronto 950 or 970.

As for the codes, they are in the file section on this site. If not in the NG section, they are definitely in the Pronto section