how can i use the files as midi files and be able to delete certain parts of songs off of limewire?

Limewire will help you to get the songs, the rest requires other software.
You'll need an audio editor to select the song portions you wish to keep/delete. There are quite a few free programs available. That would be a good place to start.

A free audio editor you might consider is Audacity (click on link however I do not see any Midi export options. It does have Midi import option.

I use the free MP3 Music Editor; very small footprint.

Audacity does editing and offers many more options for managing music. It compares with Media Monkey (also free). You should at least visit their home pages.