got a few questions about anonymity on the interwebz
1. When using vpn, can your ip be leaked by being buried inside the packets?
1b. if it is not leaked, how does a vpn separate your traffic from others without sending people the wrong stuff
1c. If it can be leaked in said way can you prevent it?
2. Can a vpn steal your passwords,cc#s, etc if you using https?
3. what is a secure dns, why do I need one and what is the best one (free)
When you use a VPN the ip assigned to you by your ISP is only used to create the tunnel between you and the vpn providers. You are assigned another IP which may be a real IP or a private one natted to a public. In either case this new IP is owned by the VPN company and is what all your traffic now appears to come from. If you do not have a router in the path your PC will know the actual IP assigned by your ISP to you. Software loaded on your machine may be able to see and transmit this. If you have a router then all your PC know is the LAN address given out by the router not the WAN IP and it is unlikely it can find it.
HTTPS is end to end security it is designed to stop anyone in the path from getting the info. The end machine you are connecting to though will get passed quite a bit of information about your machine and its capabilities. There are all kinds of tracking cookies and stuff that can give away information you do not like. This is not a VPN issue itself but people who use VPN are generally more concerned.
Secure DNS is used to prevent man in the middle attacks. It is unlikely you actually need one since someone who is going to try that will attempt to spoof the certificate servers. If you are worried about it just add entries to the host table and don't use DNS.