Diff and drive shaft swop..now 4wd wont work-HELP!

[Maggie]

Hallo, im brand new. Got a second gen 2.4 td 1991. Low mileage, no rust, 3inch lift. Been using it greenlaning but wanted to make it everyday vehicle. It had welded front diff and dodgy driveshaft. I took it back to mechanic that sold me it to swop diff back to original and put in new drive shaft. He took a boat load of money and did a rubbish job. Strange sound from 4wd selector and 4wd not working. Ive got locking front hubs too. The whole thing has left me broke and gutted. I was being responsible taking it back to the guy that modded it in the first place. He kept the cash and my mud tires and now doesnt want to know. Are there any good guys in Greenock or Argyll that'll help a lady out. Or any honest mechanics in my neck of the woods. I love the truck!
cheers