1. Grab an ethernet address via DHCP.
ANS - The AP is a layer 2 device and the IP will be assigned for BVI interface. if you have configured the switchport on which this is connected to to specific VLAN.
2. Share its IP with the wireless clients, either DHCP or NAT Pool.
ANS - You can configure the AP for leasing IP address but NATing cannot be done on this since its a LAYER 23 Device and you need a layer 3 or a Router to do this.
3. Redirect all incoming users to a webpage, and finally they need to be able to surf the web normally after that initial page.
ANS - Hers is the lin kto perform the same.. Not sure if the redirection works on the Autononmous APs for WEB page..
http://www.cisco.com/en/US/docs/wireless/technology/ip-redirect/technical/reference/ipredir.html#wp36493
lemme know if this answered your question..
Regards
Surendra
Regards
Surendra BG