Law / Questions about citizenship (my father was born in Poland during the second world war) [4]

Hello everyone, I have a few questions about my chances of possibly obtaining citizenship through my late father. I've read through many of the threads on this forum, and it looks like there are some regulars that are pretty knowledgeable about this topic, so hopefully I can get some advice on next steps.

My late father was born in February 1943 in Radycz, Turka, Poland. As I'm sure most of you already know, before WWII, this area was a part of the Second Polish Republic, but at that moment in time, it was part of The General Government controlled by the Nazis. Today, it's Western Ukraine. His father was born in the same town in 1899, while his mother was born in Chernihiv, Ukraine in 1909. After spending some time in DP camps after the war, they finally traveled to America in late 1949, was given Alien numbers, and settled in the Midwest. He ultimately passed away in 1995.

I have records from the International Tracing Service that show their movement around the DP camp system (all of which state he was born in Poland), as well as records (visa applications, Alien registration forms, etc.) from the US gov't for my father and his parents that say the same thing. Based on these records, it appears he was renewing his alien registration well into the 1970's. Unfortunately, I don't have any records from Poland - we've attempted to track any records down using a genealogist based out of L'viv, but unfortunately we weren't able to really find anything.

Here are my questions - first, what's the next best step forward? Obviously any records from Poland would be incredibly helpful, but what's the best way to track those down? Would a genealogist based in Poland (Krakow, etc.) be better? What are my chances of this being successful? Even if we're able to find such records, and based on my father's background, what are my chances of gaining citizenship? What issues/hurdles that I have not mentioned should I be aware of?

Thank you again for reading this long post, and for all of your input.