See the official tutorial here: Convert a Replica Set to a Replicated Sharded Cluster
The prerequisite for smooth migration is to have a config server and all requests go through mongos. Since the subject already has a replica-set, the prerequisites are already met, so there should be no problem with smooth expansion.
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Yes.
See the official tutorial here: Convert a Replica Set to a Replicated Sharded Cluster
The prerequisite for smooth migration is to have a config server and all requests go through mongos. Since the subject already has a replica-set, the prerequisites are already met, so there should be no problem with smooth expansion.