Here is what I started with:
The first thing I did was cut the marquee retainers that I ordered to the proper size. The plastic that the retainer is made out of is pretty thick but it is also brittle and cracked under the pressure from my radial saw so I ended up using a mitre box and hand saw. I cut them a bit oversized (1/32") and then sanded down the ends with some 100 grit sandpaper until I got a tight fit.
I toyed with the idea of using velcro to hold the retainer in place but the thickness of the velcro made the retainer sit about 1/16" off of the surface of the cabinet which wasn't going to work. The retainer also needs to be removable so I couldn't just glue it down. I decided to use 4 evenly spaced screws to secure it to the cabinet so the next thing I did was mark off where I wanted the screws to go. I decided on placing the two end screws 1" in from the end of the retainer and then I measured for the other 2 central screws so they would be spaced evenly. To place the holes, I measured up 1/4" from the plastic line that is part of the retainer (you can see it in the pictures).Using an awl and my trusty rubber mallet, I marked off the holes where I would eventually drill. The reason to mark the holes with an awl is so the drill bit does not slip out of place.
After the holes were marked, I drilled them out using a 1/8" drill bit as shown below. Make sure the retainer is clamped in place as you drill so it doesn't slip.
You should get a nice clean hole for the screw as shown:
At this point I ran into my first problem. The screw caps I'm using to cover the screws lay very flat and a typical screw kind of slopes outward towards the screw head. The bottom line is that there was no way that the screw would lay flush with the retainer if I didn't modify the hole somehow. I decided to use a larger drill bit and a razor blade to dig out a cone shape for the screw head to sit in.
It was kind of a pain but it worked. I didn't have to be precise because the screw caps cover any imperfections around the hole.
The next step was to cut the marquee and the plexiglass to the proper size. This was pretty easy to do and just required a lot of trial and error. Mamemarquees printed the marquee a little oversized but all it took was a razor and straightedge to cut it to size.
I also had to cut the plexiglass which I did using my router, a straightedge and a flush trimming bit. I trimmed off about 1/32" at a time, tried to fit everything in place and then trimmed again until everything was nice and tight. I wish I remembered to take a picture of my arm after routing the plexiglass. The bit actually melted the plexiglass and all the little shavings stuck to my arm - it looked like icing from a Hostess Sno-Ball or something.
Now that the retainer, plexiglass and marquee were all cut to size, I clamped everything in place, drilled out the pilot holes and secured everything to the cabinet using 1/2" screws. Once that was finished I capped each screw head with a screp cap to give it a clean, finished look.Here are the results: