In one of my interviews, I was deemed presumptuous about my perspectives in medicine, even after spending 3 years in an ER (as a tech), and 5 years in a clinic (doing path and patient care). Even though you've been in an ER, I'd caution you on making your interests in EM too strongly known in your essay. Some people in adcoms may take it the wrong way, and it only takes one bad impression to torpedo your ap at a med school. The same interviewer who nearly sunk me stressed the importance of humility and being prepared for the unknown, both emotionally and intellectually. Looking back at my practice vision statement, it's easy NOW to see why he called me presumptuous!!! Lucky you don't have to do that one, it sucked...
Good luck to you toejam! I think it's great that you want to go back to school...if it's something you've always dreamed of, GO FOR IT. Few people in life actually get a second chance...make the most of it!