The first thing is to know what Renault engine we are talking to know if 600 euros is expensive or cheap, in principle this price for the repair we are talking about is not exaggerated.
The other issue (that of the distribution strap) I tell you, it depends, the official dealers do not complicate the beard in the least and they will not walk reuse pieces that can cause them problems (in addition to that of course since they change it, they charge it to you).
If we were talking about the workshop of a colleague, that the belt put it himself, that you want to save a few hard and he is sure what he does because I tell you, there is no problem in reassembling the same belt, but usually it is not done.
All the best.