There's a couple of different parts you can get to make this happen. I"m going to assume you have a chrysler product since you said can bus. There are modules made to interface with the can bus system That will lock/unlock the doors and interface with the the car to help start it. You will still need something to send the basic commands to control the modules(which what I've seen here shouldn't be to hard). Basicly these parts are used to interface security/remotestart systems to the cars. If you look at
www.xpressdownload.com or
www.idatalink.ca .you basicly have to send a negative pulse to work the module. Hope this helps you in your system design.