We get a lot of queries about the transmission noise here! I've got a 313 with just over 20k miles on it and they nearly all make some rattly noises to varying degrees. Sometimes it can change just depending on what angle the car is at on a hill or driveway etc.
Number 1 would defo get a second opinion of another owner, if your clutch isn't slipping then it's probably fine. Don't go off any garage telling you it needs changing because the biting point is "quite high" on the pedal either - thats also normal.
Clutch life will be down to the previous owners, if its had a sensible owner with lots of motorway miles there's no reason it couldn't do over 100k, loads of town driving and a lack of mechanical sympathy will see it out as quick as you like.
Where abouts are you based?