I've heard that the coolant temp sensor can cause starting trouble when it goes bad, but I am not totally sure so you should search that. Don't buy another engine. Why would you do that? You're engine is probably good, it just won't start. Now is the time to start looking into sensor issues; faulty MAF, coolant temp sensor as mentioned above?? Don't give up! I've been in your position before. Just don't let it beat you!!