I've been a long time fan of Turtle wax, it did an amazing job at preserving the paintwork on the diesel ZX (was never painted in 17 years and has absolutely no rust). It's also what I used when I bought the 164. First thing people told me was "you've got to paint it", after a day's detailing it looked like it was painted. I will have to paint it anyway because of some rusty bits it has, I'm just waiting for summer.
About the leather seats, I don't think a "miracle" product is necessary, I think a lot of a good product is necessary. Putting too little of something that is too expensive won't rehydrate the leather.
Have you got the seats with leather and suede? I'm still thinking about what to use to renew the look on the suede. Manual says a stiff brush is enough, but I fear the suede might be too dry to do it.
I've sworn years by Mequires - the cleaner wax in one can, can't recall the exact name but the can is a purplish redish. Using this has always yeilded great results. IMNHO the secret is the ragsone uses to apply it but more importantly, buff it off. For me, soft well used raggedy toweles. For the glass, Stoner invisible glass and non printed paper towels. Here in Italy I'm fortunate in that I can get them by the 10 mile roll so I have plenty. It does a great job on the glass. I never use any of the Rain X type products. For inside, I have cloth interiors and once a year or so use a portable steam cleaner kinda thing. I have a friend who swears he uses baseball mitt conditioner on his leather. I have no clue but his seats have a feel and patina that are to die for. For the plastic bits under the hood and inside I like ArmorAll wiping cloths. Gives me the low gloss shine I want. Tires? I don't like shiny tire so I use ArmorAll tire foam spray. Gives me waht I consider a really "clean" look all across the car.