is there a special reason for using the shift register? may it be changed for another PIC? if so things will be much simple, a single serial line and not much.
No need to care about the LCD timing and all the plah plah around. SERIN, LCDOUT is all you need.

That's my own opinion but i remind to saw that LCD/shift register combination here once or two.. i can't remind where now but if you do a search, you'll find it