Chevy Silverado Electrical issue

I know some of you guys on here are truck guru's so I thought I'd post this up. Truck is a 2010 Silverado Crew 4x4.

About three weeks ago I went out to start my truck in the morning and it wouldn't crank. When turned to the "on" position it would do the bulb test as usual and when turned to the "start" position everything went black. When released back to "on" all dash power would restore. I thought the battery and charged it, then load tested. It was fine. I doubted my equipment(because it acted like a bad battery) and took it to the auto parts store and had it tested again. Guy said it was perfect(its a 10 month old battery). Worked with the dealer to troubleshoot some and traced it to the interlock/ theft system. Went as far as I could without a laptop with Chevy's software. After fighting with it all day in subzero cold I finally had it towed to the dealer. They checked it in that night and verified it wouldn't crank. The next morning the tech went out to grab the truck and it started right up. They check it over and couldn't find a thing wrong with it. There was a transponder(keys) code in it and they checked both my keys and verified they were synched currently. They basically said we can't find anything wrong so we will just have to wait and see if it does it again. They said if it does it again they would want to replace the "exciter" module, but couldn't really say why or if that would even fix the problem. I told them to change it now if it was the problem and then they said it wasn't.

So I took it home and put it in the garage and didn't drive it for a week or so. Then we took it up to the lake last weekend and as it got dark I noticed I have no high beam headlights. Highbeam light comes on in the dash cluster, but no lights. Took it back to the dealer thinking they disconnected something during their diagnostics and they messed with it for an hour and couldn't figure out why they won't work. This time they have decided the under hood fuse box has some corrosion and that must be the problem. There is no power to or from the fuses for the high beams. There is some light salt film on the top and light corrosion, but not enough to cause a solid loss of power in my mind. I am a heavy equipment mechanic and these guys obviously have no idea what heavy corrosion looks like!! So now they want to replace the entire power distro box under the hood to the tune of $400-$500, but I'm not totally convinced that is the issue. The scary thing to me is they don't seem convinced either, but just thought that was a good place to start. They said its a fairly common problem and they change about one a month(smaller dealership). So that must be it the service manager thought!!

I know there is nothing worse than owning a vehicle with an electrical demon. Been there, done that…not fun. We are having a super cold winter and it scares me that this issue could come back at any point and leave us stranded in subzero temps. Has anyone had similar electrical issues with a truck like mine?