Add VLAN vSS in production Environment

Hi,

Since we have installed VMware vSphere 5.1 in our environment, 2 virtual machines have already created and being in a production environment. But the time comes up to use advanced things like managing VLANs.

The issue is that adding new vmnics [vmnic 2 and 3] and associate them to the new vSS does not seem a problem since the network cards are newly added. In the other hand, the existing one [vmnic1] will be associated within a VLAN in the vSS created !

I was wondering if we proceed to add a new vSS --> Add VM Port Group for the vSSa --> Add 2 other vmnics  with the existing vSS and then add 3 different VLAN ID for each vmnic, is that presents an issue for changing the vmnic 1 in the new vlanned network ?

Thanks in advance !