Thanks.
To the OP....I took a quick look at the shadowboxes in the link. They are not super hard to make but to do them at that level of quality you will need some specialized equipment to produce a reasonable facsimile with unlimited creativity. There are some shortcuts you can take but you be regulated to what you can find premade in a craft store.
First and foremost you will need to find some pre-made shadow boxes at someplace like Hobby Lobby, Michale's, etc. Look for one of their half off frames sales for the best deal. Second you will need a decent mat cutter (about $100 and up) or find some precut mats that will fit your shadow boxes with some minor edge trimming that can be done with a photo trimmer. ($50 or less) Next you will need to look at getting a circut machine or buying premade scrap booking letters, shapes, etc. After that it is simply a matter of assembly. Wood dowels are great for suspending the letters to give that 3D look. They are cheep, readily available and very easy to work with.
As with anything start cheep until you get a hang of it. Don't be afraid to buy some stuff knowing that it will just be a learning experience and you will not be able to produce anything you would hang on a wall. Find a shadow box that is slightly damaged and you can get for next to nothing and grab some scrap book stuff that is on clearance, and start experimenting.