Dorrey

I'm new at this, ive purchased an 89 Odyssey, it's great. But the more I look the more I'm confused. The last owner cut the electrical plug off and just left the wire there. Can I just wire a new plug onto it, they also cut into it and added another ground going ?. I'm not real dumb, but dumb enough to ask for help. Same with water pipes, but that's after this problem. Any help or advice would be appreciated. Thanks.