I cant remember the name of the manufacturer - but I can find out if you want. If you are somewhat handy diy type you can definitely do it yourself (me and my pregnant wife were able to do most of the house over 3-4 days) Although it was a bungalow with a fairly low slope.

Also Id try to get some other prices - and look for respectable companies who have a real location -and dont just operate out of a van.
Ask them for references from other customers, and of course insist on seeing all required insurance/workers comp papers.. If they dont have it and someone falls off the roof of your house - you are liable.