2003 Peugeot 307 cam belt/ sump gaskett

hiya two qustions really, my partner was driving the car the other day and the cam belt came off(not snappes) it had been rubbing on the housing and had worn down in width. now would this have done any damage to any of the pistons /rods?? also how much would this cost i have been quoted £500

alos the mechanic said i have an oil leak (i do its all over my drive ) he said it is coming from the sump gaskett . now how much would it be to replace this..??

thanks in advance