i gathered what data i could off my family from dates ,names ,records ,anything at all to be honest when i went to speak with older member's i wrote it all down for future reference even the family stories that might have been misinterpreted later in the years each pad contained data from each surname
my grandmother suffers bad alzheimers so i gathered what i could before it was too late she was the one i spoke to first ,sadly now she doesn't even remember whose is who in the family these days

i then went through the dates and names given by family and starting cross referencing the information from the actually records i managed to get

even though you don't want to go from the start again it might be for the best to cross check all that's been done before and chances are youll have more connections with other family from records online in the past 100 years than say 2-300 years ago,
someone else may have found that data your father never got round to discovering that can push you further back ,
im not sure what it would cost for that type of search abroad but i traced over 400 years of some family for less than £50 from the scotlands people records and genes reunited
for me it was easier to start from scratch mentally than redo someone else work