#1
Are there one or two guitar parts in this song?? If it's played on one guitar, then it's extremely hard.
#2
It's possible to play solo. In fact, I feel that John Williams' duet sounds over-produced. Try Goran Sollscher's solo recording. By the way, most tabs or scores I've seen are solos.

It's not very difficult but it takes some experience to accentuate the melody and create the illusion of 2 guitars.
#3
To add to that, the illusion of multiple voicings (or parts) is one of the huge appeals of classical guitar. The tone of the various voicings are different and the multiple guitar effect comes about. It's hard to explain in words how to create the separation of voices.