Just make sure it is actually coming from that hose and not the steel pipe above it going into the thermostat housing. It's quite common for the o-ring on the end of that pipe to leak also. My FG started leaking from that pipe at less than 5000kms and I had a BA that leaked from the same seal early on in life. It's only a couple of $$ so may pay to do it while you're doing the hose.
If you have no experience in this area, I would strongly advise against it. You can cause too much damage by incorrectly installing a cam. Take it to a good mechanic to have it done.
The screen is fitted in the oil supply pipe to the turbo yes. It is located on the side of the block below the inlet manifold. To get it out you need to remove the sender unit from the fitting that comes out of the block and then remove the nut on top of the oil pipe. You can clean it out with contact cleaner or carby cleaner and refit it. Have a read about it in here. http://www.fordxr6turbo.com/forum/index.php?showtopic=32461 Some say remove it, some say keep it. I will be keeping mine as I know the history of my car and it serves a purpose.
If not inspected and cleaned it can become blocked over time, causing oil starvation to the turbo bearings. If that happens bye bye turbo bearing cartridge, hello expensive repairs. Very important to at least check it.
You can also tee it into any fitting that is on the inlet manifold, if you desire. The blow off valve tube is the easiest to do though. The gauge will read what is going into your engine if it is plumbed up to the inlet manifold. If it is tuned to 10psi that is what it should read.
Diff oil 20-50K depending on your driving style. Clutch fluid 10-20K Gearbox oil 50K (manual) Coolant 50K Airfilter (If K&N) clean and relube every 5K Rotate tyres 5K Steering oil 20-50K It's what I have and will be doing to my FG. Inlet manifold bolts 10K Clean intake pipework 10K Brake fluid 50K or 2 years.