Its possible to get the steering rack off without dropping the whole engine. You just have to unbolt the swaybar to get it to loosen up so you can move it. I recently did drop the engine in my sienna when i was doing a few repairs. What i hate about these vans is there is barely any room to work on under neath and with a Transfer case its even harder as its more in the way.I almost messed up with the crow's foot though - forgot for a moment that I needed to tighten it onto the steering rack shaft - had it turning the wrong way on the first try. I had to hold the end of the adjustable wrench (on the tie rod) and the extension with one hand and run the impact with the other - or that crow's foot goes flying!
I'm also not a fan of 'Stop Leak' - but that white pepper trick work for 10 years on my Jeep! Never had any luck with Bar's Leaks or whatever it's called. Maybe it depends on the size of the leak. My power steering fluid is not going down very fast - gotta try something. Changing that rack will cost close to $2000 by the time it's done. Too hard to do that on the floor what with trying to drop the engine cradle and all to make room to get it out. Guys have done it though, but not many pushing 70yo!