Been there, bought the tee shirt, sold the tee shirt. Expect amazing results... at first. Let me offer a few things I've come across.
The are no short cuts to changing fabric color, the sun fades even the best dyes. When I bought my Fiero, I dyed all interior panels and parts with expensive dyes. The interior looked esthetically better having a matching black tone, but the fabric felt oily to the touch and was no longer soft. Fading followed shortly after. Wear will be your worst enemy, especially in the case of the seats, with sun fade following closely behind. The "best" and only way to change the color of the interior in my book is to replace the fabric. I will post some pictures to illustrate. New fabric also adds to the new car feel, and it's nice having soft materials to graze your legs rather than oily ones.
Soon after first Dye:

Not long afterward:

So I stripped down all of the apint (a nightmare) and used real dye and new carpet

(I should say we, I had help)

After new carpet and redye with the best vinyl dye you can buy:

This stuff is the real deal for dash's and vinyl. The paint sinks in and has a simi gloss finish that really makes the vinyl look like it was made to be that color. I highly rocemmend it! I've tried about 5 other types of paint on spare interior parts. Appliance paint comes in second place, but is too glossy. SEM is the ticket.

Generic picture, I did not use blue.

I hope this helps someone. You need to do it the right way the first time. In the photo above where we stripped the door panel of the old paint: That was a 5-6 hour project of tedious peeling and scrapping.
Before painting, use Sherwin Williams (or equivilent) cleaner, oil and dirt remover; it makes for a much cleaner outcome. Apply light coats. As for carpet, you can sometimes find short black carpet at walmart! Any automotive restorative shop (converitible top repair, reapholstery) will be happy to sell you carpet. It cost about $20 for enough to do both doors an behind the seat. You can also lay down new black carpet on the floor; just cut four holes and trim to right dimensions with dampener underneath.
Be careful when doing all of this because replacement panels aren't the cheapest, but at least they're available.
Goodluck

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