I had the problem with the plug coming undone too. I would drive and my battery would drain to the point where my tach would bounce around and die soon after. I rigged it with high-temp zip ties.
Assuming you have a v6, I know you don't have to undo the axel. It makes the job a bigger PITA. If you undo your tie rod and y-pipe, you have plenty of room. Reach from the top of the engine bay for the hard-to-reach top alternater bolt, and the other one can be reached through the hole the y-pipe removal made for you.
One question for someone...this stupid mega fuse...can your car charge with it being bad? and drain while it sits?