My GTV has conked out a couple of times at idle. I'm guessing it's the dreaded MAF as it's been revving up to about 2000 revs at time whilst idle also? I've had a quote of £180 from the local Alfa dealer. Does that seem about right? An Alfa specialist in Nottingham has quoted me £90 but he says if the old one is a bugger to get off it will be £200
They are dead easy to replace... pretty much plug and play. In fact an easy way to diagnose if it is a MAF is to try a good one off the shelf they're that easy to fit. They might also need to do an ECU reset.
Labour will depend on what your garage charge per hour. It's probably less then 30 mins effort but they might sting you for a full hour if that's their minimum labour time charge. The Alfaworkshop fits them for free which gives you an indication that labour isn't exactly massive on them.
As I'm not sure if you're car is TS or V6 I'm not sure how much of a bargain the £180 is. The other one ranging from £90 to £200 is a bit worrying as £90 doesn't sound like it includes parts and £200 is way over the top for labour on it own. I am not aware of them ever being problematic to remove.