Need help identifying which window seal I need!

It's for a series 1 '79 Golf L 5 Door, basically on every door this seal is perished, also on 2 the metal section under the seal has started to rot..
The seal along the bottom of the window is the one i'm after, can I replace with the window wound down, and how hard is it to replace?
Also, what's the purpose of the metal underneath the seal, as shown in the second picture, and what's the best route with this?
Forgive my questions, i've never tackled seals before





Much appreciated,
Alex

ttt