Obedience Class on an Older Maltese

I would like to know what the chances are of training a 7 year old Maltese? I want to take her to obedience class and have her learn to sit, stay, and to be better at waiting until I get home to go potty. She is paper trained, but I would prefer for her to go outside. I bought a wire cage for her. If I use it with her, she does very well. I just hate leaving her in there. I leave her in there for no more than 4 hours at a time, but I still feel guilty. Any recommendations? What about obedience class?
--Need's better manners