I have got to the point of pulling the stem from the middle, BUt it will not come out.. I have pull very hard.. is there a tool or what should I try.. Thanks

Want to tell us what you are talking about?

Sounds like a diverter problem, If it is this may help, How to Repair a Shower Diverter on Stanadyne Faucets | eHow.com (http://www.ehow.com/how_5443946_repair-shower-diverter-stanadyne-faucets.html)
If that doesn't get it we need more information, Good luck, Tom