Q. Where can I find out which Gospel material is unique to the Gospel of John?

Probably the best way to find the answer to this question is by using a synopsis of all four Gospels, such as one of the Kurt Aland Synopses in our Reference Room (BS2560 .A52 1985 Ref.).  You can also look for a book of Gospel parallels, such as New Gospel Parallels by Robert Walter Funk, which includes all four canonical Gospels, plus a few of the non-canonical Gospels (BS2560 .F84 1990 ).