What a cracking looking car that is, always been intruiged by these big old American motors, just how unreliable are they, easy to work on I presume?
Practically bulletproof - designed to be used daily and do tens of thousands of miles.
There are, as with most things, a few common flaws. Primarily, early models tend to need a new alternator every 30-60,000 miles (heavy load on electrical system).
Later ones, with the LT1 engine, can suffer from distributor failures which necessitate a replacement every 30-60,000 miles. This, once done however, rarely occurs again.
I had one that had done 168,000 miles before its first major mechanical failure - automatic transmission dropped dead. Still, it was a relatively 'cheap' fix. A company came and collected it, rebuilt the transmission entirely and refitted it for the princely sum of £1,200. Seemed pretty reasonable. It was 20-odd years old at the time as well so had done pretty well.
Other than that, just the usual car checks and general wear-and-tear issues apply. I could go into great detail but we'd be here all day

They are old cars at the end of the day, so things may break, but get a good one and you shouldn't have too many issues.
They're not too bad to work on either - front-opening clamshell bonnet makes engine easy to access, although LT1 engined cars need their plugs changing on a ramp as they're only accessible from there. They only need plugs ever 50,000 miles roughly, so not a major issue. Most decent independants can handle them as they're not overly specialised. For example, I got a brake master cylinder changed on one by my local garage for £120.
They're not ferociously complicated either, although some models do have more advanced traction control and adjustable suspension systems but they seem without major issue, to be honest.
Some of my old ones: