Plaster or install double glazing first? (Video and pics)

[ODB]

Quick one here. Having the double glazing changed on the front of the house and there was a load of wooden cladding nailed to the wall to cover up (is my only guess) some bad plasterwork. Was done very VERY poorly (even nailed straight over the skirting boards!). I've removed it all but the walls are a bit of a state.

My first question is - should I have the walls replastered first then the new double glazing put in or the other way around?

My second question is: what will I need to tell a plasterer what needs doing? I am not knowledgeable enough (with my plastering vocabulary) to be able to describe what needs doing! Is it 'new drywall and skim' etc? I think I'll need the skirting and coving done at the same time.

Video here:
http://img24.imageshack.us/i/file15871.mp4/

Pics below (but please watch video, is way better at showing what a mess it is):

(PS I know I've asked this before but I didn't know the wall was so bad - just checking)

 

[crank39]

Install first then plaster up after, saves silly little trims covering gaps up

 

[foxhole]

Tell plasterer you need a window surround made good , currently lathe and plaster, he will replace with plasterboard.Don't worry how to explain as he will need to look to give you a price.

 

[ODB]

Perfect! Thanks crank39 and foxhole, just what I needed to know.