The problem is that there are two Catholic churches in Ukmerge and I cannot see records for the second one. What do you know about your ancestors? Maybe they come from Ukmerge district, not from the town itself?
All surnames are indeed Lithuanized nowadays from all old documents. If your ancestors emmigrated before 1920, there is a good chance they used Russianized or Polonized version, even though they were Lithuanians.