I am a technical writer with 1.5 years experience.
I also took an Arts degree in university (Sociology/Psych), so I was in your position a few years ago.
It is a common misconception that you need to have a specific engineering/science degree to be a technical writer. Traditionally many technical writers have been engineers/programmers/developers, etc. who transitioned to the role because of their expertise, but it is now more common to actually train and be educated as a technical writer, and then work in almost any industry.
The reason for this is that technically trained people (engineers/programmers/developers) are knowledgeable, but have difficulty communicating their knowledge to end-users in usable layperson terms. Technical writers close the gap by learning about a product or process from these technically trained people (subject matter experts) and then writing documentation that an average user can understand.
Education
Look into technical colleges in your area, and see who offers a technical communication program. I took a program part-time in the evenings while I worked, and finished my certificate in 1.5 years.
Keep in mind that technical writing education will teach you a completely different brand of English than university (simple, and broken into concepts and procedures), so be prepared for a bit of a shock.
Take advantage of an industry placement/co-op work experience if it is offered.
Career
Upon completing the program, you will have skills you can use in a tech writing job in any field, including writing, editing, writing tools (Framemaker, Word, RoboHelp/Flare, XML) and technical skills (basic photo-editing).
You will likely start as a tech writer, but you can progress to:
Technical Editor
Web Content Writer
Usability Consultant
Instructional Designer
Even if your career moves away from the technical communication field, you will find your strong communication skills to be invaluable in other roles.
Hope this is helpful. Feel free to PM me with questions.