You need to have a crypto image to have ip sec configuration. YOu can just check the image, if the image has k letter in it for example c836-k9o3sy6-mz.122-13.ZH.bin , then the image supports the vpn features.
and obviously you need to have adsl wic if it is other than 800 series router.
If you are using any other router like 1700 or 2600 series router then you need to have adsl wic. You dont need any NM for this.
-Deepu