I just added a 2000 watt inverter on my Sunseeker. Adding the inverter itself is a pretty easy job. I did not order a premade cable kit for the batteries instead I mounted mine where I wanted it and then had the local NAPA store make me the lengths I needed. Amazon.com has a really nice breaker box (fuse) to add between your batteries and inverter.
I did not want to run extension cords from my inverter to whatever I was using so I wanted to add an outlet in the front and the rear of the RV. This part of the installation was a little more difficult and more time-consuming. We do not stay at campgrounds so on nights that we don't need air conditioning and don't have the generator running it's nice to be able to watch TV in the bedroom without firing it up.
I would say anybody with average mechanical skills could accomplish this job fairly easy. Total cost for the inverter and all the extra parts was less than $500.