You will definately need to remove anything protruding from the playfield especially the slingshot arms or it will all end in tears, they are only 3 screws each anyway.
As with anything, preparation is 95% of the job

Yes as mentioned, remove the slingshot kickers, as well as the flipper bushes, i usually leave the rollover buttons in place and just cut the mylar later on close to the edge of the hole with a scalpel. So long as the touchups are nice and level it should all work out nicely If you're using the 3M brand "mylar" like bumper action sells, its fairly thick and absolutely fool proof to apply, and nice and shiny once the protective clear film is removed from the top.

When applying, just peel the backing from one end, and apply slowly from one end to the other, rubbing it down with your fingers as you go, as well as peeling the papar backing off as you go.

Also make sure you cut around anywhere anything screws down onto the pf, ie posts etc, and remove the mylar in these spots, otherwise the mylar WILL bubble and lift anywhere something is screwed down onto it, have a look at any of my resto threads for more info

hope this helps!! cheers... Mitch