Before you tear out the transmission try this, it's much easier.

As the shift linkage wears the lever cannot move far enough to engage first gear. If you lift the rubber shift lever boot you will see the reverse gear lockout plate. There's a plastic block that hits it to prevent going all the way into reverse. Play with the shifter and you will see how it works. The plate is held with two bolts, loosen these and move the plate to the left a bit and you should get easy shifting again. I'm told this is a temporary fix, but I have gone 2 1/2 yrs since I last adjusted it and it is just getting to be trouble again (car and clutch has 350,000 km on it). I expect to pull the transmission and do clutch in the spring, so will replace the worn linkage parts then.

Good luck.