As far as I can tell, you'll be limited to around 5 to 7 psi in boost pressure. Generally, turbocharged variants of a diesel engine have reinforced or additional rings lands on the piston. Secondly, you won't have boost compensation with the original injector pump (unless I'm missing something here) - no fuel enrichment as boost comes on. Thus the limitation in boost pressure.
Oh and I'm digressing a lot from the topic, feel free to boot me out if you wish!
Depends on how hard you want to run your motor. You can give your motor a mild tune and call it a day, but you're right, it'll take at least a day or two to suss out all the screws and nuts and see what they do, and then a couple more days to tune the thing. Tuning an NA diesel takes a full day of running and adjusting, so a turbo will take longer.
If you keep an eye on engine coolant temperature, you can control your engine's condition pretty well, but it can be dicey if you're going for mad boost and over-fueling.
As a general rule of thumb, the harder you smoke, the higher the EGT's (Exhaust Gas Temperatures) you'll be generating. A bit higher than normal or a LOT higher for a very short time wouldn't matter, but over 250 kms? I'm not sure. As a future investment, you should think of getting an EGT gauge if you're serious about tuning your engine - I would.
Personally, the way I'd tune a diesel engine is to let it smoke during boost buildup - this raises EGTs and help accelerate the turbine. As full boost is reached, it should not smoke at all, or very slightly - this will drop the EGTs down to a safe level.
Here's a topic I started once upon a time to discuss electronic diesel fuel injection, of the non common-rail variety. There'a a link in the first post that might be of interest.
Electronic Diesel Tuning Devices