Thing is...if I'm spending the time/effort/money going to WOM automotive, there's a part of me that just wants to wait until I can afford to have a 6 gear box fitted, which is my ultimate goal.
As the owner of a TDI75, you're perhaps better off converting your existing gearbox to 6-speed rather than fitting a 6-speed MYP gearbox. As such, a replaced shift tower bearing would be carried across to the 6-speed 'box, thus not wasting your efforts/money/time.
You can fit an MYP 'box to a TDI75, but the MYP 'box has a larger bell-housing to accommodate a dual-mass flywheel. The TDI75 has a single-mass flywheel. The result can cause issues with starter motor engagement. Personally, I believe an unmodified MYP gearbox is only perfectly suited to the TDI90, which has a dual-mass flywheel.
You can 'hybridise' an MYP gearbox by fitting the smaller bell-housing from your existing gearbox in order to make an MYP gearbox that's perfectly suited to the TDI75, but this involves much more work. If you're going to go to that effort, you're perhaps better going down the route of adding a 6th gear to your existing 5-speed 'box, which remains (to my mind, at least) the most mechanically elegant way of obtaining 6 gears.
Though the A2 certainly feels a lot less ridiculous on the motorway, it still feels like it should have a 6th gear.
Completely agree. My 6th gear just feels 'right'. Whenever I now drive a 5-speed A2, I really feel that something is missing.
It's worth noting, though, that the payback time for any 6-speed 'box is loooong. At the time I had my gearbox converted, I calculated that I'd have to do 120,000 miles
in 6th gear before I broke even. Of course, there are many reasons to do it besides saving money, but unless you're doing lots of motorway miles, it's unquestionably just an expensive luxury.
I remain a fan of the longer 5th setup, despite now having a 6-speed 'box. However, I'm adamant that it needs to be thought of as a change rather than as an upgrade. It's a compromise solution that provides some pros and some cons; whether or not it's suitable for you depends greatly on your use of the car.
I predominantly do motorway miles, so my previous longer 5th setup would frequently save me money due to the increase in fuel economy at motorway speeds. However, I also do a fair amount of driving in mountainous areas, where I would essentially only have 4 gears due to the longer 5th being inaccessible in such environments. In these circumstances, the longer 5th ratio would effectively cost me money. On the whole, I saved, but many A2 owners with the longer 5th find that their average fuel economy does not go up by much, if at all. Sometimes, all that's gained from the mod is a quieter drive when motorway cruising - which alone can be a good justification for the change.
Personally, I find the longer 5th is a down-grade in terms of the vehicle's 'driveability'. On a winding A-road (or in a 50mph speed limit on the motorway) I found managing the larger gap between 4th and 5th really tiresome. When doing longer cross-country routes, I found it quite draining to have to continually choose between rev'ing it harder in 4th or spluttering slightly in 5th; it requires much more concentration on an aspect of driving that's normally a subconscious process. Low-rev, high-load scenarios (such as trying to accelerate from 45mph in longer 5th) are terrible for your engine and gearbox, meaning the lower limits of the longer 5th's capabilities ought not be explored too often.
For those who use their A2 almost exclusively as a motorway cruiser, it's a very good option; compared to a 6-speed 'box, its pay-back time is relatively short and it makes driving at speed a whole lot more comfortable. But it's not without its drawbacks.
So, if I just did all but change the bearing for now, do you think that would make an appreciable difference?
It could do - it all depends on how badly worn the bearing is. The bearing could be 98% of the problem. If it's letting in water, you'll only emulsify your new gearbox oil. I'd suggest that doing everything on my list, along with cleaning out the ball joint as suggested by
@depronman, should be done in one hit. You'll probably be amazed by the difference.
No need to buy a new counterweight, by the way; I'm sure someone will have one from a failed gearbox. It's just a lump of metal, so mileage and age is irrelevant.
Cheers,
Tom
audi.7zap.com
(I think the main reason she got rid was because she wanted a new car, but her emotional attachment to the A2 meant it had to be justified). 
