If you're going to 'rebuild' the head, you'll likely be replacing guides seats and a few valves. Probably exhaust on cylinder 1, and 2 & 3 are marginal while 4 is ok. If you're leaving the engine in the car, then just get the head work done. The guide work and valve job are not the easiest to do on this engine, any competent machine shop can do it, but you have to specify the correct angles on the valve job or it will cost you power. It's not a typical 60 45 30, the top cut is a 32 degree angle.

Burned valves on these engines are typical of a bad valve adjustment. You don't have to do it often but you do have to do it, and I would say inspect them every 40-50k miles, or ~4 years of driving.

 

Yep the F series is pretty tough and is great on track, just sucks to replace one I have toyed with the idea of preemptively doing the kswap and selling my F20 to recoup some of the costs due to the price on them these days. But not sure I would do it. If I break the F20 then I will for sure look at the kswap route. Already even discussed some details with ASM on it so the thought is there!