Alright, you have presented three basic questions so I'll toss three responses back at you.
First up, the exterior. LSPs (last step products) produce different levels of depth, shine, and gloss. Megs M16 might be what you're looking for. It's a "brigher" wax, as opposed to a wax which offers tons of depth. If that's the look you're going for, M16 might be worth a shot. Unfortunately, it's not sold in the US anymore so you might have a difficult time finding some. Obviously, it's not going to transform your paint into a matte finish, but compared to some other LSPs it usually results in less depth.
If your car has leather, everything is leather - there shouldn't be any 'ette in the car. The Leatherique twins (
Prestine Clean and
Rejuvenator Oil) will leave your leather looking new as opposed to treated.
PB Leather Stuff is great for maintenance cleaning too.
The shiny steering wheel is a tricky issue. I would recommend NOT using leather cleaner there, at least initially. You need to strip the build up of oils and dirt from the leather first, that's what is causing the sheen. You could use an APC (diluted accordingly) like
Megs D103 and a toothbrush for starters. Some also have luck using dish soap like Dawn. Conditioners will make the steering wheel slippery, and that's dangerous.
Of course, prevention is always better than repair. I usually wipe my wheel down with a clean, damp (with water) MF every month or so. This removes the oils that have accumulated on the wheel and leaves it looking matte and new.