If you buy a new tank from a custom maker they will beable to put a hole in it quite easily for you or if you can't get it drilled and don't fancy doing it yourself you can get a overflow box which is basically a controlled syphon to the sump.
Drilling is very easy though, I just found out what size hole I needed, bought a glass drill bit for close to that size hole off ebay, marked where to drilled applied plenty of water not too much pressure whilst drilled then hey-presto your tank has a hole in it, hopefully a circular one!
The sump is very easy though, find out what you want to do in the sump, refugim, in sump skimmer, external skimmer, calcuim reactor etc etc the list goes on, on what you could build into the sump. So you find out what you want in the sump then design around that.
I just got some glass cut at a local glass cutters then siliconed them in place.