1997 Nissan Pathfinder Mistake replacing the battery

When attempting to replace the battery, the posts were reversed from the original battery, the cables were connected and there was a short. Now, the car won't start, no clicks, fans, dash lights, nothing.

One person told me that it could have fried the alternator. I have seen this before on older vehicles, so this makes me nervous.

Another person told me that it is probably a fuse. There is a fuse box by the batter with some very large fuses. It looks like some of the fuses have become brittle with age, so I am hesitant to start pulling things out only to have it crumble in my fingers, thus creating another problem.

How much damage was caused, and is it something that I can fix myself?