Hey my Gateway FPD1530 monitor is not working properly. I turn it on and it works. But as soon as I plug in to my computer it goes into sleep mode. Is this a power supply problem?

It goes into sleep mode if it does not get the video signal from your PC, or like you said, it may have power supply problem. We need to narrow down the problem first by trying this monitor with another PC or another monitor iwth this PC.
If it is the monitor problem, then you will need to do an in-depth troubleshooting, please read my guides first before DIY repair.

Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors pictures: http://s807.photobucket.com/albums/yy352/budm/

Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague

Capacitors kit: http://lcdalternatives.auctivacommerce.com/ he can make you a set of caps for you.
Or www.digikey.com just make sure to use caps with low ESR, 105c, high ripple current, long life rating such as PANASONIC FM or FC series.