If asked does an insurance company have an obligation to disclose an umbrella policy? If not how can you find out without the aide of an attorney?

I'm not a New Mexico attorney.  But as far as I know, there's no law that requires disclosure of insurance information, outside the context of a lawsuit.

I think you really need to reconsider your decision not to hire a lawyer for this case.  A wrongful death action is usually a substantial case, and there's a very good chance that an experienced personal injury lawyer will make enough of a difference, over taking the best that you can talk the insurance company into paying, that you (and the fund) will come out ahead, even after the legal fees.  If the insurance company knows that you aren't going to sue (and if you don't have a lawyer, they do know that -- even if you do sue, representing yourself, it doesn't worry them), they have no incentive to pay you what the case is really worth.