I don't even think it is legal to attempt to do a c-section yourself...could be wrong, but just kind of strikes a bell with me. I think I remember reading about somebody who tried a c-section on their dog and had to take it to the vet for an infection: Ended up with cruelty to animal charges and surrendering their animal. Here is a link to an article with photos of a c-section performed on a young goat....
http://www.bigredcouch.com/journal/archives/2009/04/goat_kidding.html
Okay, I have a goat whose mother was a Nigerian dwarf that weighed about 60lbs. Somehow the guy where I bought her had his 160lb Nubian buck get to her and she had a kid that weighed 4.5 lbs with zero issues. I got an accidental mini-nubian out of the deal. He has grown up to be about 120lb goat, so he is mid-way between his parents size-wise. I don't know how big a size difference you are talking about, but the kid will be larger than a pygmy, but smaller than a normal kid for the breed of your buck. The big question is what is the size difference between the two in inches of height and weight? Too large and anything other than twins may kill her, the kid, or both and even then may be problematic.
As to the vet issue....finding a vet who will treat goats can be a nightmare depending on where you live. Some areas large animal vets are easier to find than in other ones: I used to live in Ohio, not far from Amish country and had my pick of half a dozen guys. Here in SE Louisiana, I called dozens of vets and nobody would look at them. Finally, one of the vets referred me to someone (equine vet), who referred me to someone else who does care for them. This guy is super, but over an hour away.
Just a suggestion, but if your state college has a veterinary school, they may be able to help you out. Also, my vet does a lot for the local 4-H kids that show large animals, so the local extension office that runs the 4-H program may be able to help you find somebody. I really hope you can find a vet just in case. Since she has softened, you don't have a whole lot of time.
Please let me know how she makes out.