Ask your friend if there was oil in the spark plug wells. If there was, you need to have the valve cover gasket changed very soon, because if you don't the new plug wires will rot and it will start misfiring again. Also ask him if the thermostat housing is still the original plastic one. If so, get that swapped for a metal one ASAP. These things have a long history of cracking, causing overheating, and often resulting in engine damage. Both of the above are inexpensive and relatively easy DIY jobs.
And last but not least, do you know when the timing belt was changed? (i.e. how many miles ago).