I'm a bit confused about how to setup PPTP on my cisco 3620 it would make my ipv6 conf much simpler.
It looks like this might be of some help:
http://articles.techrepublic.com.com/5100-22_11-5926395.html
But why PPTP? IPSec is so much better and easier to work with. Either way you will need an IOS image that supports encryption. Additionally, having an NM-VPN/MP hardware encryption accelerator card is practically a requirement for any serious VPN implementation on a 3620/3640 series router.