This isn't a big pre TDI site but some basics:
Rust.
The crankshaft key eventually slips and lets the crankshaft sprocket spin. This will cause the pistons to hit the valves. Sometimes it lasts a long long time, sometimes it doesn't. You can use a crank sprocket from a TDI but you have to machine it to fit.
By this age, the coolant hoses will be dried out and will probably need replacing soon. Leaking coolant tank is not a good sign, it could be pressurizing the tank if there's a leak, if the head gasket was replaced due to overheating, it's possible the head deck isn't flat.
You might also want to ask at
http://www.vwdiesel.net/phpBB/ or http://forums.vwvortex.com/zeroforum?id=22 , they deal more with eco diesels and IDI diesels.
Rust.
The crankshaft key eventually slips and lets the crankshaft sprocket spin. This will cause the pistons to hit the valves. Sometimes it lasts a long long time, sometimes it doesn't. You can use a crank sprocket from a TDI but you have to machine it to fit.
By this age, the coolant hoses will be dried out and will probably need replacing soon. Leaking coolant tank is not a good sign, it could be pressurizing the tank if there's a leak, if the head gasket was replaced due to overheating, it's possible the head deck isn't flat.
You might also want to ask at
http://www.vwdiesel.net/phpBB/ or http://forums.vwvortex.com/zeroforum?id=22 , they deal more with eco diesels and IDI diesels.