My grandfather was from Lodz, Stanislaw Lebida. My grandmother, Agnuska Janus
You can start with ancestry.com and maybe some census databases. First you must ascertain when they entered USA.
There are 328 persons with Lebida family name in Poland today: [moikrewni.pl/mapa/kompletny/lebida.html. It looks like their origins are from Lesser Poland - environs of Mielec, Busko and Sandomierz.
And Janus? Janus is very common in Poland: over 11 thousand bearers now: