A Spektrum DX8 or 10T is a much easier programmable radio than the Sanwa.
It'll work alot better with 4s lipo, but maybe you being a rookie, starting with 3s may be better with slower movements.
Stairs would be too steep! it would have the power to climb that grade, but...
If I was using mine outside, I'd build a wooden box with a hinged ramp to drive the model in/out, put on rubber tires & a pull rope to haul it around. 80lbs for me is about my limit that my back can take anymore, but the overall shear awkwardness of the model's shape to grab it is too much.
I would use the servos and esc's recommended by Vario, they can source them for you & send with the kit.
Basic tools is all that's needed to assemble it.
The worm drive reduction on the swing needs to be precisely centered to work well, they provide many various thickness shims in the kit to do so. I was unaware of this & didn't know how to do it correctly & I destroyed my gears.. luckily for me I found an aftermarket bolt-on for a direct drive gearhead motor. It works much better in my opinion, but the worm will perform well if set up properly.
When assembling your track drives, file flat spots on all your shafts where set screws meet & blue lock tite all set screws!!! Can't stress that enough, it's heavy & the tracks take a beating putting alot torque on the drives. I'd also recommend that you request the 516:1 track motors vs the 256:1 motors that come standard in the kit.. slower speed - more power!
The counter weight is a hollow plastic shell; fill it full of lead shot or I used air rifle BB's.
Take your time, study the photos carefully & enjoy your build.
Where you from?