Wow, you found one, I never did come across that sound file when I searched. It's downloaded now for future reference. Please do let me know if they reply to you.
As for converting it to PS-3, A LokSound L costs less, and allows for customizing. Plus it'll let me keep all my DCC conversions under one brand. I do plan on buying new MTH PS3 locomotives going forward once I have DCC fully setup. If Lionel would just add DCC to their O Legacy locomotives like they do for S gauge, then I'd be all set.