You can find seats front and rear easily and probably not spend a fortune, if you get it and want some info let me know. As far as carpeting you can probably find that or get a place to do it, i'm guessing slightly more money and the glove box might be an issue. You could find a stero to plug in pretty cheap but I wonder if your going to need speakers too, i'm guessing they are all out. that said you can probably find a decently fast e30 with an interior for the same amount of money, and even if you don't moding it for what you want is half the fun.