Q. Does one need to wash hands and eat bread for a Pidyon Haben Seuda? Or can just eat
Mezonos? Does it override learning Torah?

A. Poskim rule that indeed the Pidyon Haben meal is a Seudas Mitzva (Rema – Shulchan Aruch 551: 10, Sefer Happarness 298, Siddur Yaavetz 29. Trumas Hadeshen proves that it is, since the Talmud (Babba Kama 80a) relates that Rav attended such a meal, and otherwise he would not partake, as mentioned in Talmud Chulin 95b).
However Rashbo (Teshuvos 1: 199) maintains it is not.

Since most Poskim are of the opinion that it is a Seudas Mitzva, one should attend and preferably eat a Kezais (olive volume) of bread. If he has to partake on Torah learning he may shorten his attendance as needed.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller, Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit’a