I don't speak polish, but i know that the Serbian č is certainly not the same as the English "ch" as in church or chimney.
This may also be so cause there actually is a difference between Serbian and Croatian consonants, so you may be confused if you go into such detail, observing the language as Serbocroatian (not that they are very different).
In Serbian, the phonemes /tʃ/, /cç/, /dʒ/, and /ɟj/ (in contrast to Croatian and Bosnian vernaculars) have an independent phonetic realization in most vernaculars.
^ P. Ivic, Dva glavna pravca razvoja konsonantizma u srpskohrvatskom jeziku, Iz istorije srpskohrvatskog jezika, Niš 1991, p. 82ff.
Gruszka - im not sure how good you know serbian, but you can try see Đ and Ž as voiced partners od Ć and Š... as in:
voiced Š = Ž
voiced Ć = Đ
voiced Č = Dž
You are right about the palatalization thing, though. There are 5 consonants traditionally regarded as "soft", and those are the palatal ones, so it could be that they came to be such by a process of palatalization.
Native: Serbian ( Sprski / BCS)
Fluent - proficient: English
Advanced: Norwerian ( Norsk)
Intermediate/Good: Russian, Portuguese
Studying: German, Korean + Wants to learn: Norrønt, Middle and Old Englsih, Czech, Frisian, Dutch