Hello Martin,
Welcome to MOM. I don't have a Ŵheel Horse myself (I have several Bolens) but it would appear that you can get the parts to keep it going. I have been told that the C series is semi professional use and would probably be more than sufficient for your needs. If it is the original engine then it should be a Kohler 12hp tractor. As you say there are a few chaps here who can give you all the info you need. Generally speaking, the Ŵheel Horse is a properly built garden tractor unlike the modern plasticity ones you can get today unless you are prepared to pay over £3500 for a Ride On. £450 or so is probably about right but as with all, especially older machinery, check it over before using prior to each mowing session. You can get a 42 or 48 inch mowing deck and there is a guy here on the forum who might have one up for grabs. Your tractor I think is from the early 1980s.
As a professional gardener, one of the things about maintaining an orchard is to time the grass cutting. Do it when the grass isn't too long and when the conditions are favourable. Also mow before the apples start dropping on the ground as your mowing deck will not able to cope with the extra debris.
Best of luck with the viewing tomorrow.
Andrew
