Cigarette odor removal can be tricky. The smell is usually in more places than you think. Even if you replace all the carpet and the seats then you might still smell it when you turn on the AC. So the key is to get it out of the vents as well as everywhere else.
When I do odor removal on a car I typically take out the front seats if I can. If they are powered then I have to leave them in, but
if you can remove the seats then it makes it a lot easier. You have to clean every surface of the car to get the smell out and some surfaces are very hard to get to because of the seats. I clean the carpet with a carpet cleaner that I buy locally called Prestone Foaming Carpet Cleaner. I have it reviewed on the site in the product review section. Anyway, they have a new version that includes an odor remover. That really helps clean the carpets. Remember to use it to clean any cloth in the vehicle. That includes the headliner and your seats. If you have leather or vinyl seats then you need to use the appropriate cleaner on them before you use any protectant or conditioner.
I use Meguiar's #39 to clean the plastics and vinyl in the car. It is an excellent cleaner that will take care of the smell on those surfaces. You may have to disassemble certian parts of the car to really get it clean. It just depends on how hard core you are about getting the smell out. Odor removal isn't a product. It is a fairly time consuming project and most of all it is a process.
Even after you have cleaned your carpets, seats, and all the surfaces of the car including the windows, you will want to shoot a couple shots of something like Meguiar's Odor Eliminator down the vents. Also, you will want to spray it under the dash where your feet are. The odors are hiding down there and will come out again when you turn on the heater or A/C. I have yet to find a better odor killer than Meguiar's Odor Eliminator.
After you get the seats back in then I would suggest that you turn on the fan in the car and put it on recirculate so that the smell can get filtered a bit. Open up the car and shoot a couple sprays of the Odor Eliminator in there once in awhile and let that just circulate. Then open the car up and let it air out for awhile. Drive around with the windows down for a day or something. If you can park it in a garage then leave the windows down overnight so it really has a chance to air out.
The smell won't be totally gone unless you can tear the whole interior apart and steam clean everything. However, this process will definitely get the job done as good as it can be done without getting too complicated. You just have to think the simple thought of "If I was a smell, then where would I hide?" Think like the smell and you'll be able to get rid of it all.
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