Great advice! We still get questions about whether or not outside research is "cheating"! Certainly not!
If you are stumped about a word such as the name of a place or person's name, a good first stop is the original document on the Library of Congress website (which you can visit by clicking the "view original on www.loc.gov" button in the transcription interface). You can also consult the in-depth Library resources linked on each campaign page. And of course additional information or historical context can be found through general web search!