Same AS number from different location and Migration of IP addresses

Hello, Is that okay to use Same AS number for the two different site on different location? as well as any good documentation or link or deployment scenario where I can find the merging of two different AS into one AS? As well as what to do if I have an IP addresses as a service provider dependent block and want to migrate IP addressing to the IANA assigned ip addresses? how can i achieve that? regards Devang Patel