Hey, I wouldn't ride the bike at all until you replace all the broken spokes. I guess you probably realize by now that riding it with missing spokes can bend your rims. Anyway, I just recently replaced a broken spoke on my rear wheel, it was easy, although it took a little time. There are two different types/sizes of spokes on your bike, so just order a few of each. They are very cheap. I think I got mine from Bike Bandit.
Take off the exhaust and rear fender, if you have one. Remove cotter pin and the 'Jesus Nut.' Remove rear wheel from bike. Let all of the air out of the inner tube. Thread a spoke through the center hub, then put one small drop of WD40 in the spoke nipple. (Be careful not to overdo it on the WD40 because it will eat rubber, with time) Push the nipple down into the rim most of the way -- NOT all the way down. Still having the inner tube inside the tire keeps a little 'spring' under the nipple, which is good. Turn the nipple with some needle nose pliers to attach it to the spoke.
I'm not sure how badly bent your rim is. You might wanna just buy a used one from someone who is parting out a bike. Theoretically, you should be able to 'true' your own wheels as well. That, too, should be pretty basic, but will take a little time. Although, I admit that I have done it to several bicycle wheels, but not yet on my Express.