yes the belt is over due a change due to its age.
one thing to consider is replacing the water pump at the same time, most people on this forum do this.
Why? the water pump can fail and its a belt off job to replace it so the extra for the water pump while the belts off is fairly cost efficient.
You will get varying quotes as some dealers will charge for two jobs.. ie cambelt change and water pump change which sperately will have alot of labour.
While others will be intelligent enough to know that they can be done at the same time.
So how much.. mm.. well most dealers will ask £200 - £300 for th service.. and similair for the cambelt change. Although doing them at the same time would be cheaper. At a guess id say £550 for a dealer is considered a good quote.
Why not go independant. Dealers are actually quite clueless. Some i know for a fact go on forums such as SCN to get
help!
Im sure a few people will come along soon with actual accurate quotes..
Where abouts are you, we could recommend a garage.