The first post tells how to change the OS. I haven't gone through the threads looking for info about Fido sim cards being fried by this OS, but if they aren't mentioned you should be ok.

As far as I know it was only an issue with this version, so any newer versions should be ok. As for where to find a non-released version, all anyone can say is you have the internet and you're looking for something. Do the normal thing you'd do in such a case and you'll be surprised what comes up.