First things first, Bauer....Welcome to Leatherworker.net!
You have found the penultimate source of leather knowledge, so be prepared to spend some time reading.
There are quite a few variety of leathers, and your choice will determine your success. Vegetable tanned leather is what is used for pieces with a lot of tooling and/or molding. Leather can be hardened several ways, the most common being heat. Leather is dipped in water, molded to shape, then dried. Heat helps set the collagens (glue) in the natural fibers. The shaping of the leather is done when wet when it's malleable. To color leather, a dye, acrylic paint, or chemical compound is used- most commonly spirit dyes, oil dyes, and water based dyes. Paints can be used on leather, but run the risk of cracking if the item is flexed much. A beautiful finish can be attained by simply lightly oiling the leather and placing it in the sun. Other options may include using Ferric Acetate, aka vinegaroon, and an age-old recipe in which a piece is dipped in a heated mixture of oil and beeswax. The result of the latter is a somewhat darkened, quite a bit harder, and very moisture resistant finish. You may see this type of finish on period knife sheathes at Ren-Faires.
After molding and coloring, the leather must be sealed to prevent further absorbtion of moisture. This is done with acrylic waxes, natural waxes, oils, or lacquer finishes. The composition of the finish helps determine the "shinyness" of the item.
I'd like to suggest doing a search for posts my member "Daggrim". He does a lot of helmets, and may be able to give you some specific pointers.