As Pointer said, a lot of recommendations depend on what kind of equipment you have access to. IMO, 3.5 acres is a very big field to work all at once with ATV class equipment, especially the first time doing it.
In any case, first thing you need to do is get a soil sample. Depending on the results, the price tag might surprise you. For example, a 3.5 acre field in my area will on average need 10.5 tons of lime, 1,300lbs of 10-20-20 and 100lbs of urea just to get started.
In my case with ATV class equipment, the first thing I'd do is mow it (or burn it) and see what needs to be done to clean it up (remove rocks, debris, etc.), then chunk it up into smaller sections I could work easier. Heck - 3.5 acres you could have a dozen different really nice small plots going in a few years.
