Don't be afraid to try cleaning it yourself. The first time is very stressful and you will be very precious about it, as you should be, but honestly, it isn't that difficult.
Blow all the dust off the mirror first. Then lightly brush remaining dust off.
Then any cruddy bits (frog poo, the bane of my life etc) Lay a couple of clean tea towels over top of the mirror and wet them, let them sit for 15min or so, this will allow the crud to soften before rinsing off, you don't want to try rubbing crusty stuff off the mirror.
Gently clean the crud off , repeat the soaking with wet tea towels if necessary.
Rinse mirror with clean water, distilled/boiled/filtered rain water, what ever.
I use a very old, well worn, clean cotton t shirt, for the drying process. They are lint free and very absorbent for those last few spots of water that linger. They leave a streak free finish.
It's best not to clean the mirror in the sun, it can be blinding.
There is a video I'll try to dig out of one of the big mirrors in Hawaii being cleaned with horse sponges and dish washing liquid. It will make you cringe.
Not the one I was looking for, but you might find it interesting.
http://www.youtube.com/watch?v=hRwcF...eature=related