I am on the starting stages of this process myself, ie replacing an aging 3005 series concentrator with an ASA. Unfortunately the only way to do it is dig in and create the configuration on the ASA device from scratch. Good old fashioned elbow (or brain?) grease and some patience seem to be the best tools.
It is known as the VPN 3000 to ASA 5500 Conversion Tool (BETA).
You send a XML version of your VPN 3000 config and your SE will need to wash it through the tool. Takes a few minutes. He then sends back the text file that will be run into your ASA to config your tunnels.
You should edit this text file as it will contain settings that may overwrite some existing (and possibly working) config.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...