93 blazer. won't do 4wd. switch doesn't light. nothin'

crawling around under it yesterday fixing another problem i saw three severed vaccuum lines near the transfer case. can i assume this is a big part of the problem? i'll fix those. i have a donor truck to get the lines and to check the routing, etc. just wondering if there is anything i should look out for and if ayone knows where those go and how to trace them. they all look alike of course so it's hard to know what is what.

any help at all very much appreciated.

Probably a big part of the problem