changing the battery isnt that hard, cleaning the games and keeping them in working order is harder!

My orinigal SMK was replaced by Nintendo for only 7$, thats after my kids played it to death and someone stepped on it and broke the Kart!

SNES carts with save files use SRAM, or Static Random Access Memory. Basically, it lets you save data to it for long periods of time with only a minimal charge to keep it active. As long as you don't save to it often, SRAM can last a long time as it uses relatively little power (as evidenced by the fact that most cartridges just use a watch battery to keep the SRAM alive). If you do save often, however, SRAM starts to wear out due to its volatile nature and requires more power to keep the data alive. Simply replacing the battery won't help much there; you'd do better to replace the SRAM itself, if you can.

Whoa, where can I get this SRAM?

I don't think you can buy the kind that SNES games use any more (there's several varieties, and of course many different sizes). The easiest way would be to basically sacrifice another SNES cart's SRAM by swapping them. And you would have to make sure that they were the right type; even within SNES carts, there were variations of what size of SRAM was used. Given the tools necessary to swap SRAM, and the inherent risk of bricking your cart (yes, you can brick SNES cartridges) or permanently damaging the SRAM/cartridge, it's usually easier to just buy a new cart unless the game is particularly hard to find.

ooooooorrrrrrrr,

Just buy a Wii and get it on the VC. Eventually nearly, all game will be there and the classic controller feels exactly like the SNES controller.

Pretty sure the battery is a cr2032. Pop the cart open and double check.