Hi Ernie,
maybe someone has already privately replied to your Email posting and perhaps you are already familiar with my suggestions that follow. If not, here they are anyway.
To comment on your last statement first: a quick search on the LDS website reveals film numbers 1538824 and 1538925 for Greiffenberg Kr. L�wenberg which include the time period you are interested in, but only for the Roman Catholic church. Though you don't specify, I therefore presume that you are interested in the evangelical (Lutheran) church records.
If so, a very real possibility why you can't find them is because they were destroyed in the war. Of course other possibilities exist: they may not yet have been filmed by the LDS church (if so you could ask there) or they may exist but be 'misplaced', in which case you need to get very lucky to find them!
So you may want to consider other avenues of researching the HAMMER name. First off, a correction: the death certificate entry for Amalie should read: "Eisenbahn-Unternehmers-Witwe". (Confusing the lower case 'f' and 's' in old German font ("Fraktur") is rather easy if you don't know the rest of the word.) This description translates to:
Railway-Entrepreneur-Widow
So you may want to acquaint yourself with German railway history of the 19th century (not necessarily restricted to Silesia) and see if the name surfaces anywhere (again perhaps a long shot).
Alternatively, you might try to follow the "von HAMMERSTEIN" trail by looking at the website for (roughly translated) Institute for German Nobility Research at:
http://home.foni.net/~adelsforschung/adel.htm#14
They appear to have quite a bit of information online and even a place for submitting research requests.
Good luck!
Michael Riedel
Plano, TX