Tom,
If you get the dome type vs the crank up type, the dome needs to be relatively level. We put ours right in the middle:
If you love pulling wire, it's a relatively easy install. Hardest part is getting the courage to run the drill through your roof the first time. If you hate running wire, might be worth the $275 install by someone that does. We installed (installing) our own, as I like everything hidden and not sure the installers would have been as pickey as me.