There are many many ways to go about it. I recommend doing a fair amount of research before beginning.
Be sure to have enough room for backflow when the pump is turned off. I have a 37g with a 8g sump and my water line rises about 3".
I would like to recommend the use of a micron sock. With such a small sump, it will do a lot to help eliminate bubbles. I find it also helps with sound and evaporation. It needs to be cleaned often, but I say all the better. Helps get that stuff out of the tank before it ever decomposes.
You should consider an 'over'-baffle. Just a sheet the water flows over at water level to eliminate bubbles. The farther upflow the better, but it should come after the skimmer.
Put a ball-valve on your return line. This will let you control pump flow.
If you're putting holes in glass, the hole should be its own width in distance away from the edge of the sheet and never closer than 3/4".
Consider using _reef-safe_ silicone grease on your bulkheads, but be careful how you use it. There are several theories on best practice.
PVC fittings in general are fairly large considering your space. You will need to plan things out very carefully before gluing. Don't forget the importance of unions. You _will_ need to take things apart at some point. Don't paint yourself into a corner. Make disassembly part of your design. But use slip fittings instead of threaded when possible. You'll have fewer problems with leaks or bubbles.
Don't forget, ball-valve handles need room to be turned, and unions need room for a hand to grip and turn.
Try not to use 45* elbows. They can be difficult to align properly and are more likely to give you accidental and irreconcilable angles than a 90* elbow.
Hope this helps, and good luck!
