Which is a better paying job Plumbing or a job like chemical engineering? And which one benefits me more?

I'm 27yrs old and have been working straight out of highschool for a while and have been thinking of going back to school. If I do go I'm interested in chemical engineering or maybe biotechnologist as one of the programs I may choose. The problem is I'm also a little light on cash and feel that maybe a trade in plumbing might not be so bad. I'm having a difficult time in choosing which path I wanna take. On one hand I really like science and i'm excited about the future of stemcells, the human genome, environmental jobs and the possibilities in alternative energy and different fuels. For me it seems like there is a lot going on in science right now but the problem is schooling is very long and I don't think I can work and concentrate on the heavy burden of school especially in these challenging subjects. And also i'm 27 and not getting any younger and by the time i graduate i'll be 31yrs before i really start a job. My other option is plumbing I hear that it pays well, they pay you to become an apprentice on the job and go to school at the same time which is okay because i would be getting paid. And i would be getting paid right away and would'nt have to wait a full 4-6 years before i graduate from college with a load of debt. In plumbing there are many ways you can branch off and do something different like pipe fitting. and in chemical engineering and biotechnology there are lots of different career paths to take as well. which should I choose? I like science but my age plays a factor in my hesitation. what do you think?