Need a little help concerning a GBC

[The Shadow Dragon]

Okay, so I found this at a Garage Sale around here:

I have 2 things I want to know. First, is there somewhere I can look up how much it is worth? I looked on Amazon and eBay, and the lowest price I found on either of them was $30 (I paid $10 for it), but I would like to have another opinion. The second thing I want to know, how do I clean it? There is a little dirt on the front. It is not that bad, but I would love to know how to clean it off. I would love any advice I can get about storing, cleaning, or gauging the value of this Game Boy.

[Hot Trout]

Foam screen cleaner, a microfibre cloth and patience. It is worth approx $20 but in enough years this model might be worth more than the normal versions.

[The Shadow Dragon]

Thanks for the tip, I'm kind of new to the whole collecting thing.

[tashmetu]

If you don't have the original box it is almost worthless. Here in Holland you can buy these Gameboy Colors (without box) for $4,- - 7,50. For example a Gameboy Micro (even unboxed) is good for $20 here!
But collecting them is fun!!!