If the pedal just goes to the floor, I would say the clutch isn't fully disengaging and that's the reason it's resisting going into gear. Check your fluid system, there's a smaller master cylinder and resovour on the firewall between the fender and the brake MC. Make sure there's fluid in the resovour (it just takes standard DOT3 brake fluid) and follow the metal hardline across the firewall and eventually over the tranny and to a slave cylidner bolted to the front of it. Check for any leaks or wet spots. It's possible just one of those (the master or slave cylinder) is going south and not holding pressure, but it's also possible the pressure plate itself has failed and the clutch has nothing to push against.