IPhone 4 back camera is glowy?

My back camera is glowy, bright, and a little grainy and of course, annoying.
yes, i know i should just upgrade since it is the 4, no, i do not want to get a new one.
it was a used one, and when i got it the camera worked fine, but now i'm noticing tiny scratches on it.
i obviously need to fix it but i also don't want to go to a store to fix it because there are a few cracks on the back and i don't want them nagging me that i need to fix it.
(no need for the comments about how i don't take care of my stuff. Thank you.)
my software is up to date i'm pretty sure
is there a *cheap* place i can send it in so they'll fix it?
is there a safe (doubt any way of having to open it myself is safe) way i can clean or fix it?
is there somewhere in the settings i can fix the brightness?

Is the lens clean?

Just replace the back cover. The cover lens are part of the back cover of the iPhone 4, so get a cheap one on eBay or something (they even come in cool colors) and it's as simple as removing two small screws on the bottom of your phone and swapping out the back cover.

Here's one I found in like 30 seconds:

http://www.ebay.com/...1143413669

Grainy pictures are usually because of low lighting, so try to get plenty of light in your pictures. Dirty lens will block light going to the sensor so a new back cover for your iPhone may help with that.

PS. Make sure to have the right screwdriver for the iPhone since they love using proprietary stuff to build their products. Some sellers offer to throw in a free screwdriver with the purchase of the iPhone back cover.