Yes, converting MP3 to Wav is possible, but, remember the quality of the wav file is dependant on the quality of the mp3 you are going to convert. I would not convert anything if it is 64 or 128 bit as it is heavily compressed and a lot of data is missing. Nonetheless, if it is something you cannot live without just go ahead, you will be hearing the music anyway.
dbPOWERAMP is more than adequate for the purpose and is one of the simplest interface available. Use Lame encoder built-in and not the Blade, Lame is the best encoder there is. The quality is also goodl. I use it for quick conversions but when I want high quality MP3's I use Exact Audio Copy/Lame to do the job.