Diesel f150 project

I'm looking to put a diesel engine in my F150, but I need to know some things first:

1) What engine will fit in it. I was thinking of Power Stroke or Cummins 600?
2) Where can I get upgrades for it? Here in the US upgrades for diesels are hard to find, but in the UK it's like a whole other story.
3) what should I do about the tranny?

What year of F150? Diesels were only installed in the 250 and 350 models. Up until about 2001 or so, the F150, 250 and 350 were very similar, so a diesel swap requires the entire driveline, engine mounts, accessories, fuel and exhaust systems, and a fair bit of modification to the wiring harness.
After 2001 the 150 was quite different than the 250 and 350, so a diesel swap is not practical.
If you must do this, use the power stroke engine.
However, it is MUCH heavier than your original engine, so heavier front suspension is required. Also your existing transmission will not fit the diesel engine.
I would suggest if you want to swap to save on fuel cost, forget it. You would likely have more money into the swap that you could possibly hope to recover in fuel savings over the remaining life of the vehicle. Sell your truck and buy a diesel model.