Couldn't even hazard a guess price wise. 1999, so she's no spring chicken. These leisure Zodiacs are PVC, so check seems as its thermo-bonded during construction. Potentially it could be retubed as the inflatable collar slide on to a runner on the hull. Check glued accessories there's no lifting.
Also check hull condition for any tell tale damage, spiders web cracks or chips.
2-stroke Yamaha is a good engine. Colour wise I'd have thought would be around year 2000. Got to be worth £1,500 to £2k on its own. Ideally you want to see this running on muffs, pumping water and a compression test to see cylinders are within 5-10psi of each other.
Trailer looks new(ish) so there's £750 to £1k for starters. When were bearings last done if your hauling any distance?
Noticed the winch post needs to be set back a bit. The last set of rollers are of the lip of the hull. Likely to cause damage otherwise if you hit a pothole.