I've had two (main) careers -- I was a journalist for 20 years, starting as a sport reporter for a local weekly, and ending as the legal affairs editor for Europe for a international news service. But I had also been a computer geek for at least as long. My Dad worked for IBM and I had one of the first IBM PCs, which was utterly useless when the family got one unless you could program in BASIC. I took a few CompSci classes in college (but got a degree in history) and used those skills often in my journalism career, even creating one of the earliest web sites (and announcing it on TBL's email list at CERN).

My second career is as a software engineer. I did it by leveraging my domain knowledge and going into R&D -- looking at how to design software for journalists to help them be more accurate and faster. For example, how to draw the eye toward areas where mistakes are commonly made and how to handle mundane things automatically. (These kinds of things are important on a news wire, where competition is measured in seconds.) Eventually, it was evident that I knew as much about programming as the programmers and things took off from there. I'm now a Principal at the BBC.

(Edit: I've been paid to program now since 2007, so I'm probably well on my way to having a second 20-year career before I retire.)

So, basically, start where you are, using what you already know. That's more valuable than you think. Most programmers know relatively little about their users, and one who knows can be very valuable.