It it to much? Who knows. Did he quote enough? Who knows. Without knowing where you are located, what kind of company this is, what the installation conditions are, what the degree of difficulty is, the type of unit and what is required to hook up to your existing system, it's almost like guessing, how long is a string.
I'd suggest taking the scope of work provided in his written proposal and calling 2 more companies and get comparable bids.