My wife has for years been an administrator in adult education which includes English as a Second Language for immigrants . There are many "advocates" claiming to help their paisans for a fee doing things that are free except a little daunting to the uninitiated. Often these advocates were bottom feeders who had a minimal knowledge of the forms and procedures. Some of them were outright frauds.
I have always had a bias against paying for something that should be free and accessible.
That said, if the VA was more consistent across the landscape and we could trust their qualifications, skills and sincere commitment to us instead of sometimes exhibiting all those habits and traits we have seen in some civil servants I would say stay away from self-styled advocates on general principle. Unfortunately many of us are standing in the middle with a road map written in some obscure dialect and weeping silently because we shouldn't be so damn lost and confused.
If this particular advocate has a track record, is literate and knowledgeable and returns your calls I would at least listen and hope but keep copies of all my own files.
My own experience relied on an all to rare VSO who had the straight scoop and really did help me out. I also relied on the DAV..
If you have doubts there is always Hadit.com and its long list of kibitzers as your backup.
With VONAPP and the new agent orange online applications we shouldn't have so much trouble but it still doesn't hurt to have a buddy as a backup. I would rather pick up the check occasionally for a table full of veterans than pay someone for a free service but, for you, that depends on whether you have a table full of veterans you can hang with.
Remember how many self-styled mortgage experts have left people homeless as a warning.
Take heart, we've got your back.