Don't be paniced into taking your car to somewhare like F1. In my opinion they are expensive and often not that good. A cluch will cost £150 ish plus the seal so that would put thier labour rate at about £100 per hour then, even if it took 8 hours, which it won't (not if you are a good mechanic with the correct equipment)
I changed my sele clutch in less tham that on my mums drive, and while i claim to be a competant home mechanic, i'm certainly no expert. You will also need to get the selespeed set up correctly after, which F1 certainly won't do properly.
Where abouts are you? someone on here may be able to recommend a good local independent Alfa garage to give you a second opinion.
As the others have said, sit tight and wait for the Cavalry.