If you haven't found your answer yet, here's what we used to do with Scout tents (these spent their not-camping lives in a church basement).
1. Get the tent out and check for holes. Using a soft plastic broom, sweep outside of tent to remove all loose dirt, etc. If you see stains, treat with a spray-and-wash type product.
2. Take out all poles, stakes and guy lines (elastic too!)
3. Turn tent inside out.
4. Zip all zippers shut.
5. Wash in warm water at laundromat using one of the front-loader washers. Pay for an extra rinse/spin cycle!
6. Take the tent out of the washer. Hang it up (high enough none of it touches the ground) in partial sun and leave all day. Check for dryness before dark!
7. Once tent is completely dry, set it up outdoors in partial sun. Repair all holes (screens too!)
8. Spray entire outside with a light coat of scotch-guard (these tents were several years old before we started). Let dry and repeat. Lubricate all zippers (we rubbed these with pencils or chapsticks, depending on what we had handy), then open all zippers and roll up all flaps. (Ventilation is important for this step). Spray inside of tent with a light coat of scotch-guard and (VERY IMPORTANT) go over all seams with seam-sealer ON THE INSIDE.
You can do this same trick with secondhand (garage-sale or thrift-store) tents too. (We were in an "economically disadvantaged" neighborhood with this Scout troop, so we did a lot of fixing-up of equipment.
If your tent is canvas rather than nylon (and correspondingly way heavier) it may be to your advantage to set it up in a stall at a car wash and wash it.
More info here:
http://www.viewsfromthetop.com/forums/s ... hp?p=25960