Yes, the replacement of the engine harness is a good sign of owner care and also is a good thing to know is taken care of, because if it had not been, the next owner probably would have needed to plan on doing it.
With the wiring harness known to be updated, the age of the timing belts is the only other really critical service history question, beyond general evidence of good regular care. If you can't get a definite answer on the last time the timing belts were changed, you should probably assume it would need to be done in the near future as preventive maintenance if you end up with the car. If the dealer is able to come up with more records, that will be the #1 thing to look for in them.
If you have a good VW specialist nearby that sounded happy to work on this car, then you are probably in luck. This engine is a VW/Audi engine, so even if they have never seen a D24T before, everything on it will look familiar to them and it will pose no challenge if they are experienced with the 4cyl/5cyl versions. All the basic design features and service principles are exactly the same. There are a couple of particular things about the D24/D24T that are a little different from the 4-cylinder engines, mainly the front crankshaft bolt installation that requires some additional special tools and techniques. However, it's not rocket science and is easily dealt with using the recommended equipment. No doubt they would be able to figure it out if they are capable mechanics in general.
And if they are lacking one or two particular tools and they don't want to spend the money to buy them just for one customer's car, you could always source those yourself and provide for their use. Several members on this forum have partial or complete sets of the special engine tools that they make available for rent or loan. See our
Tool Rental Master List.
Same goes for the factory service literature if you or a mechanic should need it: it's available for loan here, or online versions exist in several places.