as long as you completely stop replication, you can safely backup db and restore it to a new location (on the same server) if that is what you want to do.

If you are restoring it to an earlier point in time you will have to reinitialise replication.

If you are moving to a new server you will gave to remove replication from the otiginal server first, then recreate on the new server, (script it out)

If you are getting timeouts thats likely to be poor code or perhaps indexes need de-fragmenting or stats updating.