Re: A question for the experienced.
Definitely relay any injury history. The fact that you studied before will likely show itself in your practice.
You have the right attitude about just wanting to practice and not worrying about rank. I trained in one dojo and passed my Shodan test, but ended up studying in another dojo - (in the same style) shortly thereafter. But it was a different enough that I could not pass the new dojo's Shodan test - my original teacher was a little 'out of date' with the current standards, the dojo I went to had a rigorous set of standards. They insisted I keep my black belt on - I was more than willing to put the white belt back on....
I just went and practiced, as my skills migrated to the new dojo the question became - what test to take, a Shodan test, or just wait and take their Nidan test. My new teacher gave me the option. The Nidan test was pretty extensive, and I passed it and their standards.