Determine what your plan is. Do you want a one day or two day event? Do you have room to handle a lot of people? Will you need to provide meals? Planning a CubFest is basically the same as planning a big party for your friends.
The first thing you need to do is decide if you have the facilities to host a fest. If you plan a project where a Cub will have to be brought in, such as a brake job or clutch replacement, then you need enough room for trucks and trailers. If you are just having a smaller fest where attendees will just be bringing in parts such as carbs, transmissions , etc then you could have your fest in a suburban area.
The easiest way to meet other owners is to go to local tractor shows. Find Cubs that are displayed and strike up a conversation with the owners. You can also join tractor forums on the internet where you discuss tractors with other people who share your interest. The best internet source is www.farmallcub.com. That web site is loaded with Cub owners, many of which are experts in Cub knowledge.
Once you have met other Cub owners you can plan your event. Mention your idea of a CubFest and see what they think. You can keep it local by just inviting only your new found local friends or you can extend the invitation to your new network friends as well.
It is hard to say exactly what a guest will bring. Usually the host will ask guests in advance what they plan to bring so you have an idea what to expect, however, last minute changes do happen. You may have one person needing a carb repair, some one else may just bring a transmission for a gear replacement while another may bring the entire Cub for a complete tune up with valve adjustment. You can never really plan on everything that could show up. If there is a repair that simply can not be performed, it is best to let the guest know well in advance so they don't needlessly haul their Cub (sometimes 100's of miles).
Not at all. The main thing is that you show a total interest in Cubs. Your CubFest does not have to include a workshop, you could just decide you want to have a "Meet and Greet" where you discuss Cubs (or anything else). You may just want to make it a plow day or some other Cub activity. While many guests look forward to getting there hands dirty, the main thing is that guests get a chance to meet fellow Cub Owners.
Generally, the answer is no. An exception may be if something special is planned and guests are advised in advance that there will be some cost involved. An example would be if a trip to a local tractor show or museum, etc were involved that would otherwise cause a financial burden on the host. Most times though, hosts, or sometimes a guest, will set a "Donation" box in a conspicuous spot for guest to give a little to help with the expenses. The cost of food, toilet rental and miscellaneous other things can add up quick. Most regular CubFest guests know this and will gladly make a fitting donation. the
Go for it! Have fun with it!