Your problems getting into first gear are quite normal ***if*** you have
a non-syncho box. That is, first gear is 'straight cut' and has no
synchomesh on it. Rootes changed from non-synchro boxes to full-synchro
boxes during the Series IV Alpine production. To tell the boxes apart,
you just need to check how you shift into reverse. On a non-synchro box,
you move the lever to the left and up to get reverse, on a synchro box
you move the lever right and down.
If you do have a non-synchro box, you get used to it quite quickly. All
I do is select second gear briefly (to line up the gears using second's
synchro) before I shift into first or reverse gear.
The problem of dropping out of third gear is probably due to wear in the
gearbox. I haven't seen the wear myself, but others have described
either a worn shifter fork which isn't moving the gears fully into mesh
or a worn detent spring which doesn't provide enough pressure to lock
the gears in place. (anyone want to correct me on this?)
I hope this helps you.