The "exhaust fumes" may be from oil leaking from the oil return line onto the exhaust. The tube attatches to a coming out of the bottom of the air cleaner housing. There are three little rubber mounts that hold on the air cleaner housing. It's pretty common for those to break, causing the housing to shake and the tube jump off the connection.
If that's all it is, $10.00 and you're good to go. Also, the bracket that the rubber mounts attatch to might be broken,($50-$60). This can also be an indication of worn motor mounts ($40-$50 DIY or $150-$200).
However, if the turbo is leaking, pony up $1000.00++!
I wouldn't recommend buying any diesel without a PPI and compression check unless I was buying a parts car, because that's what you could end up with.
Low miles mean NOTHING if the oil hasn't been changed.
84 300SD (sold)