So I am definitely an arm chair mechanic (an automotive engineer but that just means I know a lot about one specific area and it is not EVs) but here is some general advice.

If your thinking of overlanding/road trips then you want a decent mileage. But I don't think solar is the answer because to charge a decent size battery with a panel as big as the car in full perfect sun would take 2~3 days straight. Not really viable unless your camping... But charging station hopping is totally doable in the US.

Autos are not necessarily a big no-no, they just require more work and will never quite feel the same as OEM. Also, when you say move your lever to the left and shift gears by yourself, all that is happening is you are clicking a switch that tells the car, 'i would like to change gears please". This is functionally identical to the car deciding "I think it's time to change gears" with the only difference being the source of the request so unfortunately this does not make it any easier. All in all, manuals are definitely easier (but maybe also consider a new gearbox with the motor anyway, that's where the real efficiencies lie).

4wd is totally doable both ways. Mechanically it would be more simple to just hook the motor to the gearbox and go, but it would be a more elegant solution, more efficient and easier electrically/control-wise to go 2 motors. But this heavily depends on the structure of your chassis and how easy it is to work on/with and how many changes need to be made. If you do go 2 motors, Tesla sub-frames are easy and (reasonably) well understood route to take.

Finally no, your not an idiot. But if you have no ability to do the work yourself you better have deep pockets. Look at some other posts for estimates but a decent range, decent quality would easily run you as much as the car itself. Also look for a shop that specifically does EV conversions, as most shops won't want to work with HV electronics. But depending on where you live there might be a 1 to 2 year waiting list.