With all the soiled carpets and dirt in your cloth seats, I really think your best bet is to invest in a carpet extractor. A really good and not crazy over the top priced machine I use is called the Bissel Little Green Machine.
It has some great sucking power and is cable of heating up the water nice and hot which is what really will help break up the dirt and soiled carpets.
I would also recommend what Jesstzn always talks about and that is Woolite mixed 10:1 with water in a spray botle Its a fantastic de-greaser and imho will help make that job less of a pain. If you're not going to get an extractor, then use woolite and a scrub brush for the carpets, seats and door cards. Really no need for a automotive carpet cleaner that usually comes in a aerosol can.