what can a 5110 be upgraded to?

hi, my 3310 phone recently died so i went back to the big block 5110, and i really want to upgrade it a-bit, what software changes can i make? and what extra's can i add?
thanks :D

P.S can i change the software to any othe nokia phone like a 82** or 33**?

you can change menu text and graphics and ringtones.

it cannot be upgraded to anything else, nor can it be made to work on PCN1800 if its a 5110 just like a 5130 cannot be made to work on GSM900