To check your firmware version, can you use the card that came with the camera (usually a 16-23 MByte SD card)? It will allow you do do everything CHDK related and even to take a couple of practice shots... Once you are understand and happy with CHDK--you can decide how much you wish to spend to proceed.
Such as to purchase a SDHC compatible reader and/or use 2 GB or smaller SD cards... In the US, the SDHC readers are pretty cheap ($5-$15, or even "free" with the purchase of a 4 GB SDHC Sandisk card). I realize, that in other countries, such deals are not always available.
Sincerely,
-Bill