All Beatles songs are available, free, in the MIDI (Musical Instrument Digital Interface) format, and there are hundreds of sites that carry them. Here's the one I often go to:
Now, you need the ability to edit MIDI files, as they usually come with all tracks, including a really lame melody track.
You can download free MIDI editors. Then, it's a simple matter of locating the guitar track/s and silencing them or removing them.
If you want to get more into it, Cakewalk and Cubase are two highly reputable companies that have beginner-level recording/MIDI software at quite reasonable prices. There are dozens, if not hundreds, of others out there.
PM me if you need more info.