As I usually recommend, use the “Search For” feature above. There have been many queries about career changes and plans in general, and I think you’ll find the information and advise useful.
That said however, you’ve asked a question with a slightly different slant (moving to networking). In many (smaller)
organizations, there is a blurred line between sysadmin and network admin, that line generally becomes more distinct as the organization’s size demands specialization.
What I’d suggest is that you start looking for positions that will make use of what you already know, and demand *some* stretching on your part.
Since you expressed an interest in security, I’d also suggest that you look into some of the SANS courses, read books, (Ira Winkler, most of the O’Reilly books).
Oh! and develop a paranoid-by-policy mindset!!
Don’t put off getting a college degree; do it as soon as you can. No number of certifications can replace a legitimate 3-4 year college degree in terms of the knowledge, expertise, employment opportunities and pay-scale. You should pursue a Bachelor’s Computer Science degree with a Networking emphasis from an accredited, established college; this is the surest and quickest way to attain your professional and financial goals.