Doc, Welcome.
I'd like to invite you to read some more on MUTTs at;
https://www.pakwheels.com/forums/4x4-clubs-off-roaders-suv/102122-moc-m151-owners-club-pakistan
As for your questions;
Keeping in view your profession and time at hand It would be better if you went for a restored Mutt, rather than trying to restore of yourself.
If you have the knack of mechanics then you can do most of the stuff yourself, else it'll be a visit to the doc for every flu the MUTT has 
The types of alterations depends, but if a MUTT has been converted to diesel and it has been done nicely then it should not give you any troubles other than a dead battery if not used frequently.
Parts are an issue if you go for the original condition, though brakes and filters etc are not an issue.
Every auctioned vehicle has an auction invoice with it, make sure you have that along with other papers from the auction site for registration purposes.