This is what my installer had in mind:
-Remove the damage stuff and replace as many full rows as you can with the old planks you have.
-Install the old planks until the last FULL row you can install
-get some flooring tongues (available from Wilsonart as "Slip Tongues")
-get a router bit that matches the size of the flooring tongues
Photo from Tool Home
-rout the edge of the last row of old planks
-cut off the tongue of the first row of the new planks and rout the edge
note: be sure not to rout too far into the planks - just enough for half of the tongue to go in plus a tiny amount of space for the glue.
-glue the flooring tongue into the groove you made on the old planks using just a small amount of glue. It's very important not to over glue as hydraulics will prevent you from pulling the boards tightly together
-test to make sure the new plank fits to the old plank, if it does, place a small amount of glue inside the groove you made on the new plank
-slide the new board onto the tongue you just glued into the old board, wiping any excess glue from the surface.
-tape the boards together to hold them in place
-leave it alone for a couple days until the glue dries
-then finish installing the rest of the floor using the new planks as instructed by the manufacturer
Those are the instructions as dictated by my installer. I would recommend getting a pro to do the work for you - and make sure it's a pro that has done this kind of work successfully - or selling the old plank on e-bay or amazon and redo the whole room.
Hope this helps some