I had trouble with the wall nuts not making good connections. I ended up chopping the wall nuts off and using common wire nuts instead. Works perfectly now. The wire nuts are the blue ones in my picture. It's much easier to do the work around the power supply area if you take the playfield out of the machine like I did (it's how I took the picture of the power supply). Be careful how you handle or set down the playfield so you don't damage the trunk assembly.

Since you have the Mean Well screw terminal power supply, then you already have the upgraded power supply.
Houdini 48v power supply (resized).JPG

The Houdini I worked on was an early production machine. We had to buy the updated power supply kit as well as the end of stroke switch kit for the flippers.