is there an faq/how to? the lad will do it for £30, and done hundreds of cambelts before
The BIG question is has he done alfa before? it could cost you £30 now, but could cost loads more in future if done wrong.
The engine is an engine, but the cams do not have a keyway keeping them in place like your regular motors, so if you do not lock the cams and get the timing right OR worst get too much slack on the belt, you'll end up with bad results. The balancer belt also goes on one way only.
How to is basically just to get the exact cam position, TDC on the crank and then fitting the belt, losen the bolts to tension up between cams and crank, all the remaining slack should only go to the side where the tensioner is so it will keep a specific tension.
Belt should not be too tight, nor be to loose. Basically allow for 90 degree turn max on the long side, less than 90 is too tight, more than 90 is too lose.
after that the balancer belt goes on. the belt has markings so does the guide pully and balancer shaft, they need to lineup each one to the correct place, turning the belt other way round will confuse you. incorrect balancer setup will lead to a very shaky engine. same thing here, the tension needs to be perfect. Too loose or too tight and it comes of or snaps it will end up takeing the cam belt with it and create spare engine parts for you.