no you don't have to stick to dealership, but keep your receipts. battery has warranty also. recommend deep cycle for replacement. be sure to test alternator also. start engine, disconnect negative. if car still run than alternator good, reconnect.
You don't have to go to the dealer , just make sure that the battery installed is the same size and strength.DO NOT try to check the alternator by disconnecting the neg. cable!!! Good way to fry computer.