We had a company do it for my 13,000ish items before new carpet. I don't know how long it took them to pack the books up because they did it in the summer and I was not even in town to be able to oversee what was happening, but I know they had a crew of multiple people- maybe it was 4 or 5. They put books back wrong and we had to fix that and it took like a week just to try to fix everything. If you have a week and several people, I think you can do it if you're fully prepared ahead of time. best thing to do is label each shelf and start with something like A1, A2, A3, etc and then B1, B2, B3, etc. This means that someone who doesn't understand shelving can at least understand that the books on shelf A1 go in the boxes labeled A1. It won't keep them in perfect order, but you can get them packed up quickly. The unboxing will take longer in my experience and will require time to reorder each shelf.
Hope that is helpful.
Sarah