At 71k there is a chance the plugs were never changed before, then again with those wires on it something tells me the original owner took care of the car, I am betting if they are original plugs they are iridium, with iridium plugs some are said to be good for up to 100k or so, but I do not like to leave them in there that long, I'd change them around every 50k miles, and I always use iridium, I prefer AC Delco, or NGK plugs.
As for oil I like to change mine out every 3,000 - 4,000 miles, and I use Mobil One Synthetic, I could probably get another 1,000 - 2,000 miles on the oil easily, but I do not drive daily, so it takes me a while to get that many miles on it, so I will change it out if I have not hit that 3-4k mile mark within 2 years.
Did the car ever have the lower intake manifold gaskets changed out for the aluminum framed ones?
If not IMO that is the first thing I'd do.