Why in the world do you think you need a lawyer?
Whoever is named on the life insurance, gets the money - IF there is any life insurance. GF cannot intercept the money.
If GF is named beneficiary on the policy, then she gets the money, and you cannot get your hands on it, either.
Your feelings of entitlement do not matter in the least. All that matters, is what the papers said.
You'll be looking at shelling out $5,000 at least, to an attorney - and they'll be telling you the same thing.
I can tell you, though, that anyone who's disabled enough to qualify for SSDI is not likely going to find an insurance company willing to sell him a life insurance policy. I can also tell you that life insurance polices are NOT a matter of public record, and unless you are named executor of his estate (or administrator, if he had no will) by a judge, you will have no legal access to any possible information.
There's no website where you can pop his name in, and find out if he had life insurance. It's private information, protected by the privacy laws.
You are going to have to talk with your local chapter of legal aid. Legal aid has been forced by local and Federal government to take restrictions on the types of cases they can handle. If you've received restriction of your license due to DWI, DUI, drug or other crimes your best bet is to pay the fines. You could try to look into working out a payment plan to pay on the fines but I do not suggest you get behind the wheel of a vehicle without your license being cleared.