Hi Chandru
Since tunnel-group name must match the peer IP, you should delete the tunnel-group and re-create it with the new peer IP.
Only entry is the peer IP entry in cryptomaps to change, no need to start from scratch. So what you have to do is...
1)Copy and paste your tunnel-group contents to a notepad, change the name to new address, type "clear tunnel-group oldIP" or "clear config tunnel-group oldIP" or "no tunnel-group oldIP". Then paste the modified entry in notepad.
2)Change the peer IP in cryptomap entry
no crypto map outside_map xxx set peer oldIP
crypto map outside_map xxx set peer newIP
If you like, post your current config and new IP of remote peer, and let me suggest you the exact changes
Regards