Have a look at this
http://www.pocketpcthoughts.com/foru...ic.php?t=41365
Anyway - I think it is highly unlikely that you will use all your ROM re-writtes before you decide to buy a new PDA.
As for your idea about the SD card it is a good one. I have a 1GB SD card which I install most programs on except for today plugins, media players and file explorers.
You should have a look at the tutorial section of Aximsite if you have not already done so. I think some of the tutorials (such as those in my signature) would be very helpful.
Cheers