Electrical problem HELP!!!!!

[ChevyMex]

Hi..

I was trying to test the new installation of my cargo light, since my truck is in the shop since 2 years ago the battery cables remain disconected, yesterday i tried to connect the battery cables in order to test if there was power in my cargo lamp but i did a mistake, i switched the + cable to the nehative pole and viceversa, a few seconds passed and the resitence wire a 16ga black wire started to burn, quickly i unpluged the cables but the dammaged was aready done, i burned the fuse wire. So i have some questions

1. Can this happen?, or is something i have wired wrong (i know i did wrong with the bttery cables, but is this normal when you switch your battery cables?

2. How can i replace the resitance wire, this wire runs from the junction block near to battery and is spliced to a 12 ga red.

3. It is better if i just replace the restance wire with a fused circuit?

4. did i damagged the rest of the wiring harness?

Thanks