1. Paid $3000 including tax in 2008 and $2200 in 2012 for A/C installation including electrical. The install in 2012 was through a guy who was retired but did installs in his spare time, hence the cheaper price. Houses were smaller than the one you are looking at, but current one is about 2400sqft including basement. I would bank on a minimum of 3K.
2. Dunno, but would guess 100amp