If you trace the replies given in Sept 2008 on this forum, there are some explanations of the "Tu spoczywa...", and "Pokoj jego duszy", anyway, the main info is: JOZEF PIENIADZ Uro - urodzony-born ; paz - pazdziernik-October Umarl - died ; d - dnia-on day ; mer-mar-marca-March ...
PS. Your ggrandpa's family name is very old and known in Poland, acc to Polish etymological books this family name is congominal in origin - derives from the Polish language and word 'Pieniadz' - Engl. - 'money', noted in Poland from the year 1671, from this branch are going also surnames Pieniazek (1279), Pieniazko (1387), Pieniezny (1488), Pienieznik (1497), etc. The surname location in 1990 Poland is: Nazwisko Ogolna liczba Rozmieszczenie Pienia~dz 377 Wa:7, BB:4, By:6, Go:7, JG:11, Kl:1, Ka:26, Kr:26, Ks:12, Lg:14, NS:1, Op:5, Pr:60, Rz:25, S³:6, Su:3, Sz:2, Ta:120, Wb:4, W³:4, Wr:33
= thus, mainly from Ta: town Tanobrzeg area, SE Poland (in the 1772-1918 as Austria and Russia), from where Poles immigrated to a new dreamland America in two immigration waves, in the end of the 19th/beg of the 20th century, and where the your ggpa's beloved land of his birth and childhood, and his family cradle may be located in Poland even before the 19th century.