Fair price for this?

The watch looks legit to me, at least externally. And at first glance it appears to be a nice example. You are obviously encouraged to study it in detail for yourself, and familiarize yourself enough with the market to feel comfortable with the price, because we don't know much about the watch (asking price, service history, who you are buying from, etc). And in the end, we don't know your budget, condition-sensitivity, comfort buying at auction or from strangers, level of patience, etc. In other words, we can't buy it for you.

[Edit] To determine condition, you can start by studying reference information online. Desmond's blog is a great starting point:
http://omega-constellation-collectors.blogspot.com/

For valuation, I'd suggest running recent comps on actual sales (not asking prices): eBay, auctions, forum sales.