Complex sentence: Former Kiss drummer Peter Criss was thanked for his contributions which were limited to backing vocals on "Trouble Walkin'", "2 Young 2 Die" and "Back to School".
Split into simpler sentences: Former Kiss drummer Peter Criss was thanked for his contribution to Trouble Walkin. In fact, his contributions were limited to backing vocals on "Trouble Walkin'", "2 Young 2 Die" and "Back to School".