Eh, did this the other week, it's a bit faffy but not impossible. Had to do it (amongst other things) for the MOT because the car had been standing that long, the thing had seized solid and screws/bolts keeping regulator on were also shot, so no quick fix there.
Anyway:
1. Take the front end off (front bumper and metal crash bar thing) so you have better access -and also so you can pull the old Alt out of the now exposed aperture in the front panel, and pass the new one back in through it. Also take under engine cover off.
2. Using the extra access with the front end off along with the newly presented front panel aperture, remove the front facing long bolt on the alternator.
3. The second long bolt at the back is, i will give you that, a pain to extract, but you can get to it if you've got nimble fingers and a ratchet spanner (a necessity for this job). Firstly using the longest spanner you have that fits (or using the double up trick) from underneath lever the Aux belt tensioner out of the way, as much as humanly possible so you can actually access the back bolt (you cannot otherwise) and fix the levered tensioner spanner in place with a zip tie to the front panel (you can now also change the Aux belt if you feel like it). You can now then get to and undo the long back bolt with the ratchet spanner -this may take a while as you can't get much rotation in the space for long strokes...
4. Once loosened, to actually get the bolt out of it's slot however you need to slightly drop that side of the engine by undoing the three engine mount bolts that side of the engine a small amount -not a lot, just a cm or so (prop up the bottom of the engine with a jack with a bit of wood inbetween, this will help later to push the engine back up to tighten the mount back up) -you can now slide the bolt out past the chassis arm it will otherwise not clear.
5. Pull the now free Alternator (take plugs and connectors off if you haven't already before you do) out through the front panel aperture.
6. Fix the new alternator in place by doing the above in reverse, sorted.