Slight clatter after good and hot - Valve adjustment?

[78silver]

I've got a '78 SC with 71,600 miles on the clock.

I'm still pretty new to my car having only put about 1500 miles on it since purchased. The PO said that he'd done a valve adjustment right before I purchased but I'm wondering if it's something I need to go ahead and tackle. I know the mileage driven since it probably had it's last doesn't warrant it but better safe than sorry.

I did a full tune-up on my own after purchasing the car (excluding the valve adjustment) however I've noticed latetly that after the car gets good and hot, I'm getting a very faint clatter from the engine which I'm assuming is telling me that it's time to do the valve adjustment.

I guess my question is: Is it pretty typical when a valve adjustment is needed that the engine is pretty quite when cold but begins to clatter just a bit when it gets good and warmed up?

Next question is, what should I expect to pay a wrench to do it if I can't find the time. I'm currently putting in about 60/week at work and working on my MBA at night/weekends. Finding the time may be tougher than it was last year.