kiltie,
I have a excel spreadsheet I use for my 28C. PM me with your address and I will forward you a copy. Keep in mind that the F and FX models have a few more life limited parts than the earlier models. However even those limits are quite high. There is a service letter from Enstrom on time limits, I believe it is 116R?. While I have heard some operators say that the 28A does well at sea level, the C models do so much better. The Enstrom is a heavy airframe compared with its rivals. With not much more power.
If you check Sharky's Helicopters's website he normally has an excel page with Enstrom parts and their cost. Of course the cost where you are located may vary. As for time, I can give you an answer on that as I really didn't have too many problems with mine.