You would want to allow a week.
Heck it will take the best part of a full day to remove the seats/doors/ and old interior kit.
Or do it bit by bit,if you don't mind it not matching while you go.
Its quite time consuming and fiddly around the doors and windows.
They give you a method to go by- where to start first.
And let's presume you have no rust/ crorossion to fix behind the panels and you arnt going to sort the sound proofing out too?
You could do the door panels as a starting point?
Then the side kick panels up beside the rudder bar- but this will lead into does your wind lacing strip need to be replaced while your there?
That gives you a good idea before you do the tricker window surrounds.
Have a careful look at the pictures of your aircraft on the website - will you need /want to paint around the door and frame where the kit doesnt cover?
I'm replacing all those horrid self tapping screws with proper anchor nuts and machine screws.
When you go to Find the holes behind the panel-here's a tip.
Get a screw and sharpen it to a point on both ends, screw it into the hole,hold the panel up ( to exactly where you worked out it should go previously ) and give it a hit with your hand, the sharpened screw will mark the rear of the panel to show you where to drill
Send me your email and I'll send you some pictures of how I'm getting on.
Its worth the effort though, mines going to look very nice.