I replaced my rusted 85 cab with a 91 cab, and added a hydro clutch/nv4500 in while I was at it.
you will want to strip everything from old cab and install it in a striped replacement shell.
remove dash as a unit with harness/same under hood,move the front clip as a unit with harness unplugged from firewall.
but remember JUST is a golly whopper of a word...July to Dec to get mine done 1 day a week with 1 buddy helping me.
different yrs but same idea.. check out my cab replacement post on the truck board start to finsh for some pics/tips
good luck.