Dark picture (projection tv)

I have a Phillips Magnavox 54" projection tv that is about 9 years old .I have noticed over the last couple of years the picture is getting darker and darker.I have adjusted the brightness to it's highest setting and it's still dark.I took the back off of it to look inside and you would not believe the dust buildup inside.I noticed 3 big lamps or the guns in the front and they are super dirty. Could this be my problem with the dark picture? And my other question is I know a tv has stored energy inside of it so could I safely blow out some of the dust and use windex to clean the 3 guns or lites.I'm trying to avoid a service call if I can.The tv is getting old and don't really want to start putting money into it.
Thanks for any info you can provide me.
scanode@yahoo.com