OK, I changed my oil last week, so it's all fresh in my mind. Firstly, my car is the 899cc version, so it may be slightly different. While I remember the sump plug is 12mm.
I found it very hard and time consuming, most of the time was spent on silly things (eg. finding tools) and clearing up though. I did an engine flush, although from what I've heard I think it may be best not to do it. The engine flush can flush away carbon etc that holds the engine, or block oilways with the stuff that it's flushing. I think frequent changes are probably better than flushing. If you do a flush, then I found that putting my feeler guages in the throttle stop holds the revs nicely (spent ages trying to find something to put in there).
I don't mess around with ramps or anything, I put the wheels on full lock, and stretch past the wheel to the filter, and sump plug. It's very awkward though, and I suspect that it may be harder on a sporting because they are slightly lower. I also don't let the engine cool, so that it's nice and runny when the plug comes out.
When the plug comes loose I pull it out quick, and hope that I don't get soaked. The first time I did it I was completely dry, but this week my glove was soaked (oh, and make sure you wear good gloves, you don't want hot oil all over your hands). When the new filter goes in you should put oil around the rubber seal, it stops it from buckling or twisting out of shape.
The engine's supposed to take 3.8l with a filter change, or 3.4l without a filter change. I put about 3.0l in my one, checked the level, and it was just over max
. I ran the engine for a moment, and then it settled at just below max. I left it overnight, and checked it in the morning. In the morning it was on exactly max. So I was very lucky, but it's probably best to check it after 2.5l. I left it to drain for quite a while too (while I had my food).