It is sounding like my goal of a single dish setup is not something for a newbie to be attempting. I will setup the FTA independantly from DN, so is there any point in spending the extra $ for a motorized dish?
The answer to the motor question is probably yes. You have four options, maybe more:
1. Offset FTA dish with a motor. This will allow you to receive a gaggle of satellites with essentially optimal reception. Getting the motor aligned is a straightforward process, but plan on taking plenty of time if you haven't done this before. It can be tedious for some. Motors are often finicky and may require maintenance and tweaking over their lifetime. If you experience high winds, you may have more of this because a motor on an offset dish gives the dish a lot of leverage to twist.
2. Offset FTA dish without a motor and a single LNB. You'll only be able to receive one FTA satellite. Unless there is one you have in mind that has everything you'll ever want, this isn't very appealing. It is easy to set up and cheap. You can always start here and add a motor later.
3. Offset FTA without a motor and a few LNBs. You can buy or fabricate brackets to position more than one LNB on an offset dish to receive multiple birds. Unfortunately those off-center will have a weaker signal, and with an offset dish you can't go more than a few degrees before the level drops significantly. Still, if all the satellites you want are within a few degrees of each other, this could be an option. However it can be very hard to space LNBs close enough together to get adjacent orbital positions. Additional LNBs, switches and brackets could quickly approach the cost of a motor.
4. Toroid dish and multiple LNBs. A toroid is designed to pick up many satellites over a broad arc (around 40 degrees) with very little loss. Technically speaking you could put DN LNBs on this dish if you wanted to have only a single dish, but these need to have reverse polarity. The wiring for DN and FTA would still be separate. The use of toroids is very polarized. One either hates them or loves them. I'm in the latter category although I have motorized dishes, too. I've found toroids a little easier to setup than a motorized dish, and it's very nice to be able to instantly switch without waiting for the motor. But they are more expensive and you'll need a bunch of LNBs and switches to select the one(s) you want. The spacing of LNBs for adjacent orbital positions isn't as tight as for #3, but if you want to line up the LNBs every 2 degrees, you'll have to be creative. There are several threads on these forums that show how.
Most would recommend #1 and I tend to agree. However if you really want to have only one dish and/or instant switching, #4 would be a close second for me. Either way, look at Lyngsat and see which satellites you want to receive, and check that you have good visibility to the ones you want. That may help make the decision for you.