I got the slimline fixed up with a standard ku lnb, and i got the dish mounted and locked in on galaxy 19. I scanned in 140 tv channels and 35-ish radio channels. I'm sure I will lose them more quickly when the weather is bad, but I'm glad I was able to make it work.
A couple tips for anyone else wanting to try this: Before taking the Directv lnb off, I fashioned a sort of jig from wood. Then I could use it to make sure I had the new lnb in the exact same place as the original as I tried to come up with a way to mount it where it needed to be. I also set my elevation and skew before taking the dish outside. Once I went out to put the dish on the pole, it only took 15-20 minutes to get it pointed where it needed to be, locked down, and scanning in channels.
I'm sure there was some luck involved, but it really ended up going pretty smoothly.