Once you have the new NIC installed and addressed on the same subnet, the HIT kit should start using that NIC w/o change.  I would suggest that you run the Remote Setup Wizard and select "Configure MPIO" to make sure that ONLY the iSCSI Subnet is in the include list.  All other networks should be in the exclude list. 
I have an EqualLogic PS4100.  My server is connected via iSCSI with a single path.  I am going to install a second network card so that I can use MPIO.  I have alreasy installed the Host Integration Tools and configured MPIO even though I am currently on using a single path.  Once I install the second NIC do I need to reinstall the integration tools and configure MPIO again or will it automatically work once I assign the new NIC the proper IP address and connect it to the san network?
Adding a second NIC to use MPIO