Most therapists generally help YOU figure out what's best, where you do the work really and they act as an objective mediator, keeping you on track and stuff. So specific experience isn't absolutely necesssary, BUT...
This subject is so ODD to most people, it can really help if the therapist knows what you're going through, and can warn you of the common mistakes and dangers.
AND, if you want HRT eventually, the therapist is supposed to diagnose you as having GID or transsexualism, or at LEAST a written letter saying that HRT would benefit you.
AND, if he or she doesn't have any doctors she works with, finding someone who will respect her letter and prescribe hormones might be tricky.
Still though, it may be better than NOT talking for now. If you find an experienced therapist in the meantime, most will allow "credit" for prior therapy.
For what it's worth, my very first therapist was a psych who had limited experience with GID. When he focused on discussing SRS during the first visit - and started slowly squirming under his chair as we talked about the procedure - I figured I'd best find someone else

Kate