Hi tech,
I use Quantum's Long Life oil in my PD150, I always get it from TPS (using my mates trade account), it's not the cheapest of oils but it's what the guys at Midland VW used on my car the first time I took it to them for a service and they highly recommend it and I've never had any issues with it.
As for the cambelt, if you've never done one on this engine before I'd leave it to someone who has, took mine to my mates garage cuz he doesn't charge me for labour and he'd done his own golf's in the past and watching him I didn't realise how much of a job was involved, took him around 3 - 4 hours.
Also if you do decide to do it yourself, be prepared for being provided with the wrong parts if you go down the oem route (again TPS) as for the PD150 engine there are 2 kits available, the more common one, used on around 95% of these engines and then a less common one, I brought the common one, as most people would and then realised around 4pm on a Saturday afternoon that it was the wrong kit and I actually needed the less common one, of course we didn't find this out until the old belt had been taken off and the car was in bits and because TPS were closed it had to stay on the ramp for the weekend.
Regards
Noel
Regards
Noel