Transmitters
Just FYI, transmitters can be had in FM or AM in both 75mhz or 27mhz - the modulation does not determine the frequency.
zoeybadm-
This will not work for you, sorry. AM typically will not work with FM crystals and vice-versa. AM is AM and FM is FM, no changing. Same with frequency, 75mhz crystals will not work for 27mhz units.
harrynuts-
I got nearly the same deal you did on eBay... $170 for a 75mhz JR XS3, including the blue custom wheel, JR travel case, all the batts (NiMH), two servos (standard), the receiver and a transmitter charging jack/receiver battery charging jack. Everything works great and I am very happy with the deal. I caught it within the hour it was listed - totally lucky. And to top it off shipping was free. Life's good.
-SlingItX