They can use a lot of oil or none at all -- seems to be a big range of variation. Depends on how many miles and how worn out they are.
Tips if you want the motor to last:
1. Don't overheat it. Make sure all cooling components are in good shape.
2. Make sure the front timing belt gets changed if it needs it -- engine will implode if it breaks so if in doubt get it taken care of. If you have it changed, be sure to have it done by someone who has the correct tools and know-how, or if you do it yourself, make sure you know what you are doing. This is the most crucial job on the engine and if done wrong, at best it will run crappy and at worst it will blow up.
3. Make sure it is properly tuned -- cam and pump timing set correctly, cold start device functional and properly calibrated. That's it as far as tuning these engines, and you only have to do it every 75,000 miles... but when you do it, make sure it is done right so that you can really not worry about it until the next 75k rolls around.
4. Make sure all glow plugs are functional, and always replace dead ones right away because leaving them can shorten the lives of the other plugs and cause serious starting issues, even if there is only one plug out.
5. Use good diesel-rated synthetic oil, whatever is your preferred brand. AMSoil and Lubro-Moly are my favorites but Mobil 1 TDT/Delvac 1, Rotella Syn, etc are good choices as well. Use a good filter (Mahle, WIX or Mann). Then change it every 5000 miles, no need for 3k changes with syn.
If you do all of those things, it will be an extremely efficient, reliable, and cheap to own engine and will outlast anything on the road. If you neglect them, it will turn into an unreliable, expensive PITA and die an early death. Sorry if I am being blunt.
These are great engines that don't deserve the bad rep they get, but they are only great if maintained right. They got their rep from people thinking they could get away without doing the key things listed above, and then when the poor abused motor died an early death they blamed the car rather than recognizing that it was their own fault.
It would be a good idea to cover all the basics above before considering +T stuff. However, I know how it can be to live with 80hp and how nice a turbo can be. The big immediate stuff is just making sure the timing belt doesn't break and using good oil. The rest you can worry about over time. +T might be an OK idea as long as you keep the boost down, use good oil and keep it cool, and don't run it hard for long periods of time. If you put a turbo on it then try to drive it up a mountain pass, it will have issues.
Congrats on joining the Volvo diesel cult! There are not many of us but everyone else doesn't know what they're missing.
Where are you located and how many miles on the car? I used to have a 245 Diesel and miss it often. Slow, but something about them makes them fun to ride around in anyway...