First, you can retake the GRE. Before I took it, I bought a CR ROM from Kaplan (I think) and studied that. I took both the pre-test and post-test, and after completing the course of study on the CD, I increased my scores by at least 15-20% on every section. I ended up doing very well on the GRE itself, so I strongly believe in these study programs. Since most programs require 1200-1500 score on the GRE, retaking the test will be necessary.
As for your age, I've said elsewhere on this topic that I knew of a CRNA who graduated from the Texas Wesleyan program when she was 55 years old. I myself did not start my program until I was one month shy of my 40th birthday, so age is not a problem.
The letters you asked about are important, but selection committees look at them knowing you are only going to ask people for recommendations if you know they will give you glowing recommendations. So, they are helpful, but rarely are they the deciding factor.
There is a shortage of nurses, and there is a shortage of nurse anesthetists. Unfortunately, this does not translate into a shortage of applicants for the limited number of school seats in anesthesia programs, and competition is tight. So, as I have said before, do everything you can to not give the admission committee a reason not to select you.
Kevin McHugh, CRNA