Firstly, the clutch linkage is not a good design. OK when in in good condition but when any or all of the pivots wear it gets very sloppy. Lubrication doesn't stay there very long. Can mean that the pedal works it differently each time. Could also mean that when things get warm down there the rear gearbox mount sags a bit and makes things worse. Linkage check worthwhile, but once worn it's replace or build up the holes with weld etc. Not checked the VP list but a new set of rods/levers a possibility.
Synchronisers are in the box so not checkable without dismantling. Select 1st with engine at lowest revs. If it doesn't want to go in, select 2nd and then go into 1st. No synchro on reverse so don't try to find it when you're rolling. Some modern cars have a synchronised reverse gear. Very few people will want to get into 1st gear before coming to a stop so double declutching not really needed. You dip the clutch - put it in neutral - give the engine some revs so as to match the engine speed after you've changed down and then dip the clutch again at the same time as selecting the lower gear. Best left to old trucks with no synchromesh at all. A bit of a lost art.