Assuming its not a complicated database with any kind of encryption
1. Back up the database. Use native or third party compression tool
2. Transmit and apply the back up , any related login scripts, linked server, jobs et al.
3. Test the restored back up functionality et al
4. Daily or hourly restore of differential back up . (Log shipping can be set up also if you can make changes to ur server).
5. On the day of cut over,
a. Stop the Prod server.
b. Make sure there is no untransmitted records on the publisher to distributor/ distributor to subscriber
c. Stop all the replication jobs - Publisher/Distributor/Subscriber
e. Transmit and apply the final compressed backup on the ToBe server. Apply any changed logins/ et al.
f. Restore MSDB for all jobs
g. DNS changes.
h. Start all the replication jobs
The pain will be if replication errors out, the snaphot will take longer for the 100GB.