is there any mods you can do to make the go 300 turn into a 500 or a 700

i was just wondering if there were any mods out there to convert the tomtom go 300 into a 500 or a 700. software would be differant i used ham radio and there are always mods for these new radios pressing buttons or even taking it apart to take a diode out ... i will be updating the card to a 256 i have a 32 meg at the moment and i have a card reader. if i put the card into my card reader and copy all the files and then put the 256 card in and paste back onto the 256 is it going to work or am i going to get probblems like other people are having with tomtom not being able to read the new card. also are there any free downloads for the tomtom . i have the camera and the extra voices but was just wondering if there were more maps and other things i could put on. there are a few things on my tomtom screen which as crosses on them
cheers
spuddy