1993 f150 standard transmission not shifting after transmission drain and fill.?

I couldn't get the fill plug off so i needed to go into the shifter and fill it in through that. it shifted fine before and now wont go into anything but neutral. i had to take the shifter out to fill transmission back up. when i put it back in and tried to push it into 1st gear it wouldn't budge(except for neutral) so am i s.o.l or what do i do?