I would definitely get midnight blue seats (they are everywhere, if you are doing SVT seats that is)and dye those instead. Going from a light color to dark is supposed to be difficult and doesn't produce good results.
I used a kit from leatherique. It included cleaner, conditioner, dye stripper, and dye. The size I bought was supposed to be enough for a full interior, but I had a TON of everything left over. I recommend getting the 2nd smallest kit if possible. condition, clean(might be backward, I forget) sand lightly with dye stripper, brush on dye. voila!
I've only had one little spot rub off on the rear seat that I have to redo. It's weird because people rarely sit back there and that happened whereas I'm in and out of my driver's seat every day and it's holding up perfectly. I must have prepped it poorly or something.
The leatherique.com people were extremely helpful while I did the whole process too.
For the money spent, it looks good enough for the look I want and I was quite happy with the results. Reskinning seats is an option if you want it perfect, but a VERY expensive one. I got everything done for less than 300 including seats and dye kit.