After soda spilled on keyboard, i did what i could to clean/dry (opened back plate only). It turns on and works in all...

Is there a guide for getting into the keyboard membranes for cleaning from inside? I have problems with permanently pressed alt and shift key after spill. All work with external keyboard. But i am hesitating to take it all apart withput guide. (cleaning keys from above dodnt help.) Are there spare keyboards for sale if a cleaning fails? Do i really need to do anything about resetting PRAM or something? Thanks for help!