I can’t answer all your questions but the bit of knowledge I can pass on is as follows:
V12s can be serviced but I don’t think V8s can. In any case,when I asked about it I was told it was a major faff and someone promptly sold me a LH V12 for a £5.
Once they are on a wobble they’ll be fine for miles and miles and miles after.
Err.. that’s about it. Soz, probably not much help that