I’m a lot more knowledgeable about western history too, but I did some digging on the Mukden Incident & I found some sources that hopefully you find helpful.
1st, I have an article from Encyclopedia Britannica that gives an overview of the subject & talks a little bit about Prime Minister Wakatsuki Reijirō’s reaction to it.
2nd, is an article from World War II Database. The site was founded by WWII enthusiast C. Peter Chen & is listed on the Library of Congress E-Resources Online Catalog.
3rd & 4th, I have articles on how the Incident effected American-Japanese relations from the US Department of State & www.globalsecurity.org.
Finally, from the Japan Times, I have an opinion piece by Jeff Kingston, a professor at Temple University’s Tokyo campus about how the Mukden Incident is remembered in Japan today.
If you find any of these sources unreliable, let me know & I won’t send you anything more from them. Good luck on the episode!