Not much i think, the sticking camera to windscreen is the same, what will take the longest is routing wire around windscreen, and thats also the same you have to do for both cameras.
Ar you going for a hardwire to the fuse box, or do you just go for a normal install using the cigarette lighter on the dash ?
No matter what i still think it should be done in 1 hour or less, i can do a install in my little Suzuki in under 30 minutes, and that include ripping off the plastic trim on the A- pillars and tucking wire out of sight really good.
And when i tapped into my fuse box for a expanded power grid in my boot it did take me 20 minutes or so, but only cuz i had to try out 4-5 fuses before i found one that was not live all the time.
And not least the location in the foot well where my fuse box is and the fact my back is no longer the most flexible and pain free back, and off course i did this along the curb at my friends house.
And then routing the + wire out back to the boot was pretty easy as i did so along the floor and down there i have more cheap plastic trim to push/route the wire under, and then i got the 12 V minus/ground from one of the bolts holding the rear seat in place.
Too bad there is a ocean between us or i would do it for you for a ice cold can / bottle of Coke
PS: If you go for the cheap mobius make sure it come with a stick on mount, cuz it may also come with a suction cup mount and even without a mount at all.
If you can i would go for the SGZC12RC it do have better low light recordings than the mobius, and like the mobius you can always put it in another window if you upgrade your front camera down the line.