copy tags from mp3 to flac and other questions...

[so_la_la]

Hello
I have a collection of largely MP3s (100gb) plus some Flacs and other 'minorities'. I am usingthe FLAC format  more and more as it is easy to use both in MB and in LMS which I use to pay my music through my amplifier. I have some of my FLACs stored in a backup folder only with limited tagging. These are the files I want to start using.

I wonder how to organise music I have both as mp3s and flacs. I though I need mp3s in case they will be synced to my phone. Either I convert them on the fly (as of now, MB simply copies the .flac-file to the phone) or I will need two versions of one title.
My questions are
a. how can I setup the converter in MB? I don't seem to be able to do it?
b. how can I copy tags from mp3 to flac files so that I will have copies as identical as possible (I know that this will be difficult and not a 100% possible?
c. how can I search and replace easily playlist entries pointing to .mp3s with the .flac-version?
Thanks for any answers!