Tamz. remove pump after draing down (10 mins at most)
remove return manifold ( 10 mins at most)
replace new PRV ( 2 mins??)
replace above components! ( i'll give you 25 mins ( not required) )
I get to 47 mins............Or if you remove and push the gas pipe to the side it will take you ten mins if you can get your fat fingers (like mine) in!
The thing is, you shouldnt have to do that much work to replace a prv. Its making a 10 minute job a pita.