It's REALLY easy. No need for a mechanic at all.
I'd say, give it a good inspection and cleaning first before buying one. A magnifying glass might help to inspect the wires.
I can't remember the price of a new one right now, but I can look it up.
edit: MAF for 2.0liter engine from fordpartsonline.com $144
MAF for 2.5 liter engine $192
