Hi Dave,
yes...mud is your friend!
The good thing is,now you see where improvements need to be made and what could be done to make things easier to clean for the future.Or switch to track racing
Concerning your oil problem: A possible reason (that I am certain of) could be that your crankcase ventilation is not sufficient.On my old car,I´ve had a very similar problem before and I enlarged my crank case ventilation to an AN-16 and a larger breatherbox.After that no oil pressure problems and a decrease in oil temps also,but most important,no more oil leaks from the valve covers or elsewhere.
Mark