Ok, watched the video, have some answers:
1 - YES you NEED new tires!!!!!! YIKES!!!!! Anything over 7 years old is in need of replacement!
2 - What a beautiful piece of history you have! THAT is a go-anywhere, do-anything bus! If you are serious about converting it into a 4X4 home, read up on what others are doing with their buses on the site. The issues they come up against - with me it's heat in Texas at the moment - and the solutions that they figure out will save you lots of time and $$$.
If it were my bus, and I was planning on living in it full time, a complete rip-the-walls-down-to-the-outside-metal-from-inside is the way I would go. The complete picture of what you're up against will come to light. The needed repairs/sealing/water-proofing requirements will be self-evident at that time. I'd save the overhead shelves and re-use them to help with storage. Storage is a PREMIUM on any bus, and yours in particular. If you want to keep the windows, that's up to you. Me, I'd replace them with better windows and block out any unneeded windows with steel and seal up the seams. The more insulation you have the less energy required for A/C in the summer and heat in the winter. In this case more insulation is best.
Those are my initial thoughts. Things like electrical and plumbing will come later. Getting started is the most important step.
GREAT start so far!
Firearms stand next in importance to the Constitution itself. They are the American people’s liberty teeth and keystone under independence. — George Washington