Hi - I have had some experience using TAG Heuer Switzerland. Firstly, they will always service the watch regardless. As to replacement parts they will need to assess what you want replaced and what they have in stock. You will therefore have to rely on good communication and in my experience thats where it can go wrong. I have been lucky in one case (Autavia 2446 GMT) and got a new dial but they replaced the hands with service hands. Rather ugly and they will not return the original, replaced parts. The work they have done for me has been excellent. The waiting time is between 4 and 8 months (UK). Cost is another matter however the bulk of that is made up by the service and as I said, that is a prerequisite. As suggested, look for a replacement dial and parts elsewhere and do it yourself. The post some before and after pics.
regards
Paul
www.heuerworld.com