That gyro looks old.... it would most likely need a engine teardown and all new gaskets and crankcase seals installed.
It may need several various updates on the airframe itself, one being the Center Line thrust upgrade, which is a semi expensive undetaking
that has a old " ultraprop " prop on it. Piece of junk.... That should probably be replaced with something newer, safer, and more efficient.
And lastly the guy LIED to you when he said it was already a drop keel.... That is a bone stock, " Classic " , lowrider aircommand.
I wouldn't give more than 3-4 grand for it, assuming it has a good set of rotorblades.
Depending on what the trailer looks like, maybe another 500$ or so for it too. More if the trailer is special, such as enclosed or very nice.
Your going to spend about 600-1000$ on the engine to get it tore down, inspected, and put back together with the new seals and gaskets.... Another 2500$ or more on airframe mods, plus your time..... 500$ on a new prop..... Probably another 500$ on some basic instruments..... and then you have a gyro that is safe and airworthy.