Hey, Cityboy. Good to see more GA folks here.
I am assuming this field was in planted pines. I went through the same process on a 100 acre plot that was clearcut about 25 years ago. We hired a local contractor who did a good job with a pretty good size dozer, first with a blade, then with a root-rake to windrow the stumps. A good operator can leave minimal holes with a dozer. Pine stumps aren't that hard to get out of the ground. I realize that you are probably in the Piedmont area with more clay soil. (what county, by the way? I'm guessing somewhere north and east of Macon)
I believe you may have underestimated what it is going to cost. Beware of an off-the-cuff estimate. Some of these guys will "camp out" on you if you let them. I'm not saying they're necessarily dishonest, but they may not want to scare you off with a more realistic estimate. Remember, machine work at $60 per hour figures to close to $500 per day. Does he think he can finish in 10 days?
Lime is a factor. When I run into a situation where 4-5 tons per acre are recomended, I usually try to spread it over about three years. In my experience, the ph will come up just about as fast with one-and-one-half tons per acre for three consecutive years as it will when applying it all at once. Spreads the cost and gives you that deduction for three years.
What kind of grass are you going to plant. The hybrid bermudas are great, but expensive to plant. If you are going with bermuda, don't overlook common. It responds well to fertilizer, makes a very thick sod for those hillsides, and costs a fraction of what a hybrid does to establish. I bet you already have a lot of common around the edges. If so, and if you go with a hybrid, you better kill every sprig of the common. If not, you will wind up with a very expensive field of common bermuda, because it will overtake the hybrids. If you are going with something other than bermuda, you still better kill all of the common. It outgrows everything but Kudzu.
Tractor and equipment. You can get by with a smaller tractor, say 40 to 60 hp, as long as you match the equipment to the tractor. Four-wheel-drive is very desirable, but we got along without them for a long time. I would get a 60 to 80 hp tractor, a good sprayer, a good (read very heavy duty-no junk) harrow, and a good rotary mower. A heavy-duty chisel plow is a wonderful tool for pulling up those small chunks of roots the dozer leaves. I mean a real chisel, not those smaller things you see at the tractor yards. You can buy a good one used at most farm auctions. A loader would be nice, and to use it for keeping the windrows pushed up when you are burning them would be fine, but I've seen several good tractors ruined when people tried to use a farm-tractor loader in an industrial or forestry type job. A farm-tractor front-end, even a 4wd front-end, just isn't tough enough for a lot of the jobs people use them for. Unless money is no object, I would rather spend it on a quality harrow and mower than on the loader. A good dozer operator shouldn't leave you that much loader work.
The cheapest way to do it is to just leave the stumps, get a tractor that you can harrow and mow between the rows with, burn it every chance you get, scatter some common bermuda seed and harrow it in. Use the sprayer and 2-4D to control most of the weeds and some of the brush. Use Remedy and Grazon herbicide to control the tougher brush. You can establish a bermuda grass pasture suitable for cattle in 3 years this way. All but the largest pine stumps should be rotten in 5 years. If you want a horse pasture sooner, fence out 4-5 acres to clear with the dozer, and you can probably establish it in two years.
Sorry for the essay, but it is late, and I ain't sleepy yet.
By the way, I'm in Taylor Co.