Don't know of a guide but have done the whole process using the information on the PyramydAir site schematics and the attached PDF.
It wasn't difficult to disassemble but it is hard to know which o-rings belong where without the attached PDF (which lists the size for each location)
Some of the o-rings are challenging to put in place - possible but not easy.
My gun had catastrophic leaking after a safety plug popped at 3400 PSI while filling - apparently causing a cascade of o-ring failures.
I then found that quite a few o-rings were dried out and brittle or cracking as well as some that had become square and others that had chips out of them - I was leaking from many locations.
The o-rings and a little cleaning did seal the gun back up to better than the it had been new - holding 4500 PSI for over a week.
The other part that was leaking and wasn't an o-ring was the actual shot valve - the plastic valve and the brass seat both had some damage and leaked slowly. I was able to remachine the seat back to a smooth and polished surface and it worked out OK. That valve stem was also quite rough and not moving freely in the o-rings - it was mostly dry and loosened with a little polishing and silicone. At high hammer spring settings and high power tunings, I think that the firing valve takes a bit of a beating - I will be going back in to look at it again as I reach the 3000 shot point. Putting a balloon over the end of the barrel overnight makes checking the shot valve fairly easy.
With fresh o-rings and careful tuning, I have been getting 8-shot groups with +/- 1 FPS - even running that consistently, some slugs and pellets just don't seem to like the barrel - giving wide shot groups even with very consistent speeds but other tunings and slugs and pellets are giving consistent 1/2-3/4" groups at 165' (50M) outside - and I don't have a sturdy bench or steady hands.
View attachment AVXTACT Diagram.pdf
