Stuck trying to fix a shower faucet handle/valve

The other day my 2 year old son tore off our faucet handle (single-handle) in our shower. I took apart as much as I could and found out that the screw from the handle had broke in 2 leaving some of it lodged in the piece sticking out (cartridge?). I looked online and in some books that recommended removing retaining ring or bonnet nut, before I can remove the cartridge. However I don't see any of that. This is what I am looking at, sorry a little blurry.

http://picasaweb.google.com/john.towell/Shower?authkey=mm-UDo1BenE#5287320202769218466

http://picasaweb.google.com/john.towell/Shower?authkey=mm-UDo1BenE#5287320430536470018

The white thing with the caution sticker in back is some sort of plastic protector. It is warning about soldering and heat.

My plan was to replace the piece that had the screw broken off in it. However I am stumped on how to get this piece out. Any ideas? Or other ways I could fix this? I guess I could try and drill the screw out? I haven't done that before though and didn't want to make the situation worse. Seems like a shame to call a plumber to fix a broken handle?

Piece of cake. Link is to the exploded diagram for your Moen Positemp. Turn off main water, remove Retaining Clip, pull out cartridge. Do not get repair kit. Get a new 1222 cartridge, available everywhere.

( Your particular model does not include the stop valves shown).

http://www.moen.com/shared/pdf/2353pt.pdf

Thanks so much Jimbo for your quick reply. I removed the retaining clip but the cartridge will not budge. I have put a lot of pressure on it trying to pull it out and nothing. Can you think of any reason why it wont come out?

They do get stuck.. go to the hardware store and purchase a moen cartridge tool. This will run you 10 for the generic, 30 for the moen brand tool.

Thanks for your help again. We got it out. My wife helped me get it out

Moen

Aren't wives wonderful things to have around.