Need Head Gasket - What Else Should I do?

I just found out that my head gaskets need replaced due to leaks. While the cover is off, what else could I have done? The car's got 80,000 miles on it. Timing belt and related service was performed at 67,000, and I'm assumiing the plugs were changed then. Is there any service that I could do to improve performance (ie horsepower, reliability) since the engine will be opened up? It's a 2.5 liter, 1997 Legacy GT. I've got about $500 to blow on this car, besides the head gasket job.
Thanks,