If the hammer worked properly before the field strip, then it sounds like the hammer strut was not properly installed or the hammer was in the wrong position during assembly (I believe I did this once). I would field strip it again and follow the steps in the guntalk-online link above. Pay attention to the correct hammer position and hammer strut placement. Rugers are a pain to reassemble properly the first few times. And, yes, I need a rubber mallet to remove the barrel and then to allign the bolt stop hole on the barrel and receiver on reassembly.
I clean mine each time it is fired. I don't like the gunk build up from firing a few hundred rounds and absolutely do not want to go to the range and futz around with the gun because I've not cleaned it.