Sorry to be the bearer (sp?) of bad news, but I found it to be VERY difficult to go from programmer to DBA!! I had passed the written portion of the MS DBA test, but w/out much practical experience, failed the practical. I posted to several job boards (including Craigs list) offering FREE work in exchange for mentorship from a certified DBA - no takers. Offered free work to several non-profits - no takers. Somebody explained it to me pretty well (may have been Andy Warren at a SQL Saturday, which I agree to be HIGHLY recommended).
A DBA has the potential to REALLY screw things up and most companies are reluctant to "trust" a newbe to that kind of "experience". If they are going to have a junior DBA, they are going to promote somebody with company (MAYBE industry) experience to the role. My suggestion, go back to geology and during the interview process try and get a commitment to promotion to the role. IMHO and good luck.