I don't want to tell you things that don't fit your circumstances. Are you living in a house while working on the bus, or are you living in the bus while working on it?
You could tear out your floor, but at this time of year that would likely mean some cold feet for a while. I'd guess that depends on how quickly you could work on replacing the floor. I'm pretty slow working by myself.
What I like to do is make a list of the things I want to change in the bus, then prioritize. Almost everything you work on overlaps other projects you'll also need to work on, so some projects get partially done and have to wait on something else to get done first if you get things out of order.
Honestly in my opinion, the best bet at this time of year would be to work on getting mechanical issues up to snuff. I'm not sure where you live but I'm going to guess that it's cold. You can't really paint in the cold. You can perform mechanical services this time of year and that will help to make sure you don't have mechanical problems since you will be driving at times. These buses are great for picking up supplies.
If you're living in your bus one of the first things I'd do is get some styrofoam insulation panels (1/2" @ $7 per 4x8 sheets) to cut and put against the windows to help with heat loss. Curtains just don't cut it for stopping heat loss.
I originally bought my bus in October of 2015. I left the interior panels in until the next spring so I didn't have to deal with the cold through one sheet of metal. My first winter was more of a survival experience. It's not that terribly cold being in a OEM bus over the winter, but I found insulated coveralls do help a lot and make pretty good pajamas. I use a very small electric heater now, but previously I used two heaters plus propane the first winter.
All this time I thought most people removed their ceiling and wall panels first. That's an experience. It's pretty much up to you what you do first. I left my floor in because it is covered with L-track, originally to be able to secure wheelchairs. I'd like to put insulation under the floor, but I didn't want to take a chance on loosing the L-track if I got to lazy to put it back in.
Your choices should depend on your living situation. Living in a bus while converting it is relatively miserable in good weather. At this time of year, so close to the holidays and snow, I'd work on the mechanical aspects until the weather was a bit more cooperative. If you're not living in the bus I'd say go for it, do the floors, ceiling panels or whatever you want first. It's mostly just a bunch of manual labor anyway. The work gets boring, but trips to the home store wake you up. It's a long row to hoe to get one of these things done. I thought I'd be done within the first year. You should be using your bus fairly regularly in order to keep it in good working order. That's another good reason to do the mechanical issues first, to make sure you have a good dependable platform for the rest of your build. Doing the interior work only to find mechanical issues later would be depressing.
I got rid of my Impala and use my bus as a daily driver, except I don't go out daily. This bus can sit for a month and still crank right up. I've felt very lucky. I designed this bus thinking I'd be a snowbird, but here I sit waiting for snow at the end of the second year of slow progress. Yes I could drive to SoCal anyway, but I've got to many vehicles to just leave them here on the ranch while I'm down south.
Out of curiosity, where are you planning to use the bus? Around your current home or are you planning full time travel?
