yeah come to think about it, I am sure the Specialist will only want to do the LP surgery, since it's both legs too!
Hopefully he can give you some insight on that growth.
Also, since you will be having all the pre-blood work done for his LP, your general Vet for the neuter shouldn't have to re-do it.
Also, check out:
Friends of Animals | Spay/Neuter Certificates Request
Put your zipcode in and info in and they will email you a list of Vets in your area that will except there Neuter Coupon ($64 for male dog neuter)