You should post picture of the detailed interior as well on that eBay ad.
I sold my GT 4.2 last year through webuyanycar as I started to look for my Ferrari as I couldnt be bothered dealing with deadbeats, who just wanted to get a free ride.
They offered me 29k for it which wasnt bad at all given that it was in October - post summer - and the car had 41k miles on the clock. I then sold my non stock OEM MC exhaust separately for an extra £1k.
You should try them and see if they give you a decent price, and consider selling your expensive upgrade separately if you still have the stock