the subframe will need to be moved to access the sump gasket. The gasket is £15 from dealer. Garage should be charging no more than 2-3 hrs labour. Straight forward DIY if you have ramps
Are you sure its the sump? and not just the oil filter housing gasket. I did one last week and it looked like the sump but was the other as mentioned. Only cost £5 from dealer and will take you 1hr to DIY