Hi John
A couple of simple checks on the stiff gear shift issue. It should be easier.
Check the gear shift trunnion mount on the left hand side of the engine near the fuel tank. Was this renewed and is it aligned ? The later trunnions have a PTFE center which slides on the shifter shaft better than the earlier brass stock ones .Make sure the shaft is moving easily and clearing the corner of the engine block in all positions.
Did the shop disassemble the gear stick mount and clean and lube the ball mount at the base of the shifter mechanism in the center console ? That can get stiff when it has not been used. Also check the shifter gearstick shaft and make sure it is not too grooved from the gate - they can break off it it gets too deep especially with a firm shift .
Does the firewall boot look like it is at mid rest point in neutral ? That can make the shift feel firm on either the forward or rear shifter positions on the shift as it gets overly compressed and stretched if its not centralised.
Also check if the ZF gearbox shift shaft receiver box on the top LHS of the gearbox has been cleaned internally and regreased. Old grease can certainly gum it up on the shaft and make things feel real stiff.
How was the shift into reverse? That is usually the most difficult to get working properly. DId it grate going in ?