any program for converting WAV and deleting invalid information on iTunes?

i have my iTunes library huge sized songs as WAV,but sometimes i'd like use iPod to listen to them and the problem is i can't put the whole songs from my iTunes onto my iPod because they are around 200 GB. So i want to make a WAV convert to MP3 that would be smaller sized that fit my iPod. Besides,i have ever mistaken my music duplicate for each song in my iTunes and then i took long time to delete them one by one but they are still there as invalid files-when you play it they just jump to the next one.How can i delete all those invalid info and make my iTunes and iPod tidy and neat? Is there any program for this? can i solve these two problems with one program or anything close to it with one or more programs?