You don't need a special tool to remove those clips. Simply pry them off with a screwdriver and the old ones are reusable -- they should just pop back into place.
As far as the impact strip goes, all I remember was that mine was very easy to remove/very straightforward, so I don't think you need anything more than a screwdriver. If you break a clip, they're very inexpensive from the dealer.
Prepping the bumper before painting it? I'm not sure how you should go about it. I would imagine sanding it down with some coarse grit sandpaper to remove some/most of the old paint, then a fine grit to smooth it out.
'91 300E, 208k miles