I already have a 2TB box and 1 mini. Looking to get 2 more minis for the kids bedrooms.

Am I right in thinking you can only watch on 3 screens at the same time? can that be the main box + 2 minis, or 3 minis at the same time?

Is there a self install option rather than paying an engineer to come out for 60? When had the original mini installed, was only aa matter of connecting it to the network with the WPS button?