I always hated the way Nissan designed the car so the Positive post of the battery is next to the fender. Twenty years ago, I started buying my batteries with the posts reversed. Now the Neg. is where it should be and Positive is safe and sound. Just for safety's sake, you should inspect the wiring harness both in the engine room and the going into firewall.

Auto parts stores sell a package of two rubber covers, a red and a black one, that fit over the post connectors on the battery wires, about 2 or 3 dollars.

Previous owner set my car up for a GM side post battery, never changed it. No posts on top = no problems!