That is a 4'x8' sheet of plywood you see there.
What you can't see is the chassis underneath the plywood.
Weather permitting, I have moved that sheet outside on saw horses for easier accessibility. Then back in when done for the day.
For the amount of time spent on the harness it's hard to say. I've had only a few opportunities to spend more than a hour at a time until just recently. This for me makes it difficult to come back later and quickly pick back up where I left off. Taking time to review the videos and ramp back up again. Plus the 2005 SC harness is different than the videos, having to figure out how to sort those issues and extra wiring. Base model wiring looks to be far simpler with less circuits to start with.
I'd say I've spent roughly 20-25hrs so far.
For me, it's a lot easier to work on the wiring continuously, multi hours a day until it's done. If you have a couple of free days together you could easily knock it out.
On a side note. Since you have a single car garage, wrap the front upper shock mount with towels, packing foam, something. Otherwise your shins will start to have dents in them like mine.