Changing the bed of a printer

Hello,

I recently bought a used printer, and I've consistently had the problem of filament not sticking to bed, or sticking to nozzle and no amount of cleaning, or leveling helped. I wanted to upgrade it to print ABS, and someone suggested to get a CR-10 bed for higher temps but I'm not sure how to start the whole thing. I know I will need to check my PSU, if it can handle this amount of charge, but I would also want to install a PEI sheet for better adhesion. My current printer has a 30x30 bed, but will the new bed also have to have these dimensions? Thanks for any help.
Printer: Anycubic mega x