If its like the 145 (and I think it is!) its easy enough. The 145 has a small pipe running from the throttle body to the top of the expansion tank. This means that if you get any air in the system, it comes through this pipe and into the expansion tank, so you don't need to worry about bleeding it.
If you do decide to do the job (and I would recommend it, I think that doing basic maintenance on a car is a great way to keep an eye on it, and stop little jobs turning into big ones), a few tips;
The clips which Alfa use on their hoses are sods to get off. There's a knack to them which I haven't got. I found the easiest way to pull them off is to use mole wrenches to grab the roll of metal that's exposed, then wiggle it in a twisting motion until it fatigues and breaks off. You'll need a spare new jubilee clip of the right size to replace it with.
If you want to flush it, ideally you would pull the top hose off the radiator as well as the bottom, the put a hose pipe in the bottom and wait until clear water comes out of the top. Personally, I'd pull off the bottom hose, and if its fairly clean looking just top it up once, drain, and then refill.
When you drain it, leave the heater in the hot position, then leave it hot until you've got teh system bled.
When you fill it, use deionised water rather than tap water, especially if you live in a hard water area.
When you fill it, do it fairly slowly - maybe over 10 minutes, let it settle once in a while to avoid airlocks. Put the right amount of antifreeze in first - 40% is probably enough, then top up with water. When you reach the mark on the expansion tank, slowly go around all the flexible hoses, squeezing them in turn a few times to "burp" any air out of the system.
Top it up, run it and watch the water temperature which should go up to 80C ish, drop a bit, then stabilise at 80C. Have a cup of tea, when its cooled down top up to the mark and go for a drive