anyone have experience replacing internal batteries in snes carts?

[Samus Aran]

i just bought FF3/6 recently, and while i do also own it on GBA, i sure would like it if my snes version actually saved. it seems that its battery isn't just dying, it's completely dead, kaput, no power left to speak of whatsoever. i say this because when i go to save, it can't even save when the game is still on, let alone the save still being there when i turn it back on later. you press A on a file, it makes the save noise, and...there's nothing there.

IN ADDITION, my chrono trigger cartridge makes a completely corrupted save with random, often nonsensical information...which is gone when you turn the game back on anyway.

it just had to be these two very important catridges that can't save. most of my other carts are doing just fine. but these two squaresoft behemoths have just up and died.

so if anyone here can at least mostly guarantee that they can replace the batteries with no problems, i could totally send the cartridges to them and pay them a couple bucks per cartridge or something. and i mean only a couple, because i could do the same thing with estarland for only $6

yes i know i could probably do this myself easily enough but i really don't have any non-saving, easy-to-find cartridges to practice on, and all costs considered it would probably cost me just as much if not more considering i don't have the batteries, the tiny screwdriver thingy, or a soldering iron.

anybody?