The one thing I think most important with a music collection is to convert it into a LOSSLESS audio format with info tags embedded that are accurate and useful to YOU. Some call that archiving. (Don’t think that tag info automatically downloaded from the internet will be accurate!)
With that done, it is trivial. quick work to _ transcode _ to whichever audio format you want on your player; your tags will be preserved! You can re-encode with newer codecs, to a different quality rating or to a format that is good for another player. For example, currently, Ogg Vorbis is best quality vs. size on the Fuze and Cowon players, and Nero lc-AAC is the best on Sony and Apple.
I don’t use Windows Media Player.
Programs I use include:
Exact Audio Copy (to rip and convert to FLAC)
MP3Tag (to edit tags from above)
foobar2000 (to transcode to Ogg Vorbis)
Winamp is popular with many, and deemed easy to use.
Those are freeware, but a beginner might find dbPoweramp especially simple.