Its true that you will have to install the secondary site again. However its not a major worry as your client data for the clients reporting to Secondary would have got replicated to Primary DB.
Kind of yes, kind of no. Client data is always submitted to (and of course stored in) the primary site DB. Using the word replication here implies that the data is replicated from the DB on the secondary site to the primary site DB -- this is not at
all correct. That may not have been your intention with your statement, but use of the word replication in a ConfigMgr context implies (or least will be interpreted by many as) DB replication.
The spirit of you statement is correct though.