FWIW, and for how long it takes, I'd yank the engine. That way you know there's no chance for a screwup, leak, etc, and you aren't beating yourself to death doing it. I'm kind of a large lad, so I try and avoid any fucking around in vans if at all possible.
I have seen a guy do it in a van, but I'm not sure how he installed them.
Like Matt said, does it need an oil pan/dipstick tube insert?