eh, the old car issue aside (I fail to see how working on older cars is easier than newer cars... quite the opposite, really. the newer stuff is full of computerized diagnostics. I mean, the computer won't solve all your problems, but good god, have you ever tried to rebuild a carburetor? adjusting the 'richness' of your fuel air blend? oh yes I like the computer, and the OBD system.) it really is a straight time for money play. For the basic stuff, it's pretty easy to get to the point where it takes you as long as the mechanic will charge you for (most mechanics charge 'book rate' - e.g. how much time the book says a task will take rather than how much time it takes them. It's not too difficult to get up to that speed.)
So really, for any given car, if you work on it yourself, you shouldn't be spending much more time than what the shop would charge you for the same work, and, uh, like I said, $90/hr post-tax isn't something most of us sneeze at. (Of course, if you can sneeze at that, good for you!)
that said, right now I'm taking my vehicle to a professional. the thing is, sure, the car only needs something once every 6 months, if you don't count oil changes (which I usually take in, just 'cause it's worth twenty bucks to not deal with the oil) - the thing is, where I am now, maintaining a garage would cost me more than just paying to take my car in. So yeah, it doesn't always make sense.