Have a magnavox 47mf437b no picture has green power light, removed back panel and inspected power supply borad, no obvious problem althought 2 diode ? appear to have gotten hot board is discolored from heat. tv is less than 2 years old , should i replace power supply borad? could problem be diodes/

Please read my guide first:
If you are going to DIY and have proper tools, electronics knowledge, and know safety precaution then please read on:

Please see my basic troubleshooting guide here:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
Failed TV and Monitors: http://s807.photobucket.com/albums/yy352/budm

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

Parts: www.shopjimmy.com
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.
Or www.digikey.com just make sure to use caps with low ESR, 105c rating such as PANASONIC FM or FC series.
Please post back what you find.

Replace the main power board, would be the best way