I think it's important to start learning about these cars long before you start looking to buy one....it sounds like you missed a good opportunity IF it was a good car..and that's a big IF. IF it has been properly maintained and is in good shape then they are quite reliable, but repairs are expenses...

Lambo dealers are usually not the best to work on these cars...you're better off finding a specialty car shop...other owners in your region are most helpful with this. The dealer guys (most) have only been trained on the new cars. NO clutches don't have to be changed at ten thousand miles....they get replaced when needed...came across one that needed a new clutch at 1800miles, another (my friends) still has original clutch with 30,000km. Depends on the driver. if you like to do burnouts, or stink at driving you'll be on the low end...if you can let the clutch out at 1200 to 1500 rpm then it will last you a long time. So apply power, all you want, after the clutch is fully engaged. Chad might not agree, but I'd say they really are NOT do it yourself cars. Small things, if you like to tinker, you could expect to easily do, but in general only you can determine your own comfort level, but most owners have Most of the work done...
Clutch prices are not ten grand...however, since the engine and trans comes out, it is usually a good idea to do many things that can only be done at the same time, or are just easier to do with the engine out. SO,
Plan on maybe just a clutch change for 5,6 or 7 grand (depends on shop and condition of parts, plus 2 grand for all the extra stuff that can be done at the same time. Good tires are hard to come by and there are a few other parts that aren't made anymore so they are Very expensive, but many other parts are just from other cars, BMW, Fiat and the like and there are often discussions about cross referencing parts.
The big thing you will hear about is get a PPI... a prepurchase inspection. Find someone that knows and works on these cars and pay them to inspect it before you buy it...start looking for these people and shops Now if you are serious. A ppi is the best thing you can do, also try to find an owner in your area, maybe the guy who bought this car, and try to learn from that person what it's like to own one..... other than that, don't forget the high sales taxes you will need to pay on the purchase price and plan to keep 8 to 12grand on the side for repairs as they come up..... also I think it's safe to say that every car will need something after you buy it... a few new knobs, maybe a manual or toolkit, maybe a spare tire or car cover. So plan on spending a thousand on a few small things after your purchase (400to 600for the ppi).
Good Luck
by the way, if your thread falls behind, add a comment (nicely) to keep it active......not everyone on here with advice is on here weekly. Plus there are other forums that you can also learn from.
(and Yes, I do own a Countach)