Quoted from pinball_ric:

Do not play the game until you get at the very least a protector for the castle shot. The clear WILL crack almost instantly (I learned this the hard way). I'd say get all the protectors you can.

Quoted from pinball_ric:

I have all of the protectors listed on Cliffy's MM page at http://www.passionforpinball.com/mm.htm plus a couple others that probably aren't on that page he offers (I don't think i saw the protector for the drain to the ball trough on there.) Email him and he can help get you sorted with what you need for MMr.
For the castle area I use the protectors from Mantis at http://www.mantisamusements.com/mminstall.htm
I would avoid the merlin hole protector from mantis as I had trouble getting mine in and eventually ended up breaking it. It's very soft aluminium and you have to bend it to get it in. I bent and unbent it too many times trying to get it to sit right.
At a minimum I'd say you need the ball eject, trough drain, and the 2 castle protectors but strongly suggest getting all of them. They're expensive but they're definitely cheaper than a new playfield or having to have the playfield clear coated again.

Quoted from zacaj:

Readjust the flippers to be at the correct angle if they're too low

Quoted from Ronnie1114:No drilling should be required, and any disassembly is usually trivial to install them. I learned that pinball repair usually sounds worse than it is.

Quoted from LTG:

Now might be a good time to hook up with some local collectors and get a little hands on help.
LTG : )