If you confirmed you have oil pressure (you said oil went everywhere) and the oil light went off, you most likely have pressure.
(I would think that its pretty hard to have 0 pressure. Especially with those 2 things above)
I assume you're concerned because your stock guage is not reading anything. If thats the case,( and you're sure there is pressure) you missed connecting up the guage. Its a small plug that plugs into the oil filter housing (or around there) I missed connecting mine as well. (or as Matt said, could be a faulty unit, but check connections first) There are two connections, one for the light and one for the guage.
Lifters do not cause low oil pressure. Lifters are also rarely "screwed". At least not totally and not all of them.
As far as sounding like a diesel, I dont know. Empty lifters at startup would sound like that. From your post, thats my guess.
There is proper procedure for installing new lifters (or reinstalling old ones). Lifters should be empty of oil for startup. They will be noisy for a few minutes until they fill up.
Have a look at
www.vfaq.com if you have not already.
As everybody has said though, confirm you have pressure. If you do, its probably just the lifters being noisy for a few minutes.
