Nice looking GTV!
I would be willing to be any money that the gear issue will be the "Top Hat" bushes on the linkage (a V6 only problem).
I sold my V6 on Saturday and as I thought the gears were getting progressively more "sticky" (there was resistance when moving the stick side to side in neutral and third was sometimes tricky to find), I changed these bushes on Friday (£1.19+VAT each from Alfa and there are two of them). Dead easy job, took 15 minutes all in. Remove the intake pipe to give yourself easy access then undo the nut, remove the shaft, take out the old bushess which will probably break as they will have gone brittle, clean out all the powdery aluminium corrosion from all round the area, spray with WD40, apply multi-purpose grease to the shaft and re-fit with the new bushes. When you get in the car, the gear level will feel extremely tight if youve greased in up well, but then move it up and down the gears numerous times and it will free itself and then will become perfectly slick and like new. If possible, have someone spraying WD40 on the linkage while you're moving the stick or vice versa.
Really simple, cheap and quick job and will make a world of difference.
The bush and housing below the stick is what you'd need to change if you had the exact opposite problem (very limp and sloppy gearchange).