Is the $40 for you to send them your ELM323 OBD converter and they send you the unpdated ELM327? Or do you pay $40 for just the ELM327 chip? My understanding is that they will just send you the chip. If that is true, then you will NOT be able to just unplug the ELM323 and plug in the ELM327. The circuit is comletely different and will NOT work. You will need to redesign the circuit.
I am doing my Senior Design project using the ELM327 (at least I've started the research).