There are ways of getting out grease stains without the extractor but it will take longer. Here is what I would do:
Spray a strong carpet cleaner into the stains (I actually would use the 4 star stuff because it is powerful and a good price)
Scrub like a mad man with a stiff brush or get the scrub adapter for the PC and turn up the speed.
Blot the stains with a white towel (do not rub)
Wet vac the carpet really good.
Blot the carpet with a white towel.
Tip, when you spray the cleaner into the stain, let it penetrate the grease for about 10 minutes, and the hit it with the scrub action. That should help break up the grease. Also vac up as much moisture as possible to prevent any stains from wicking back up.
Show some before and after pic if you can.
Good luck
matt