Plan for 6 - 10 hours (6 if you don't need to retrofit the oil filter housing). I was lucky enough to find a shop that would cap off at 8 hours regardless on how long they took.
If you need to retrofit the oil housing, it is a daunting task. The intake manifold needs to be removed and if you are an xi I think the sub frame needs to be dropped.
Also mentioned above, pressure testing is important so you should plan to have a shop do the testing if you have DIY'd it.