However did you manage to scratch the insides of the viewfinder?
For dust, have the focusing screen removed carefully then then blow air inside the viewfinder assembly to remove the dust inside. (Do not clean with cloth or anything -- just air). Same with mirror: just air.
For the scratches, If its the outer part, It's called "eyelens" If I remember correctly and the coating can be easily scratch. It can be had for about 20usd at ebay. Problems is how to replace it yourself (or even to find someone who'll replace it locally) so sending the whole camera for repair would be best.
If somehow replacement is not possible and the haze is intolerable, you can do the McGyver method: brushing ever so lightly the coating with a tip of cotton buds dabbed with toothpaste (I heard metal polish is better but haven't tried it yet myself so I cant recommend it.) You would of course be removing the coating this way but at least you can now see whats in front of you.