+1. Don't do the lines at your experience level. Everything else is fine if you take your time and follow the instructions. Get a brake piston retractor/pad spreader tool. You can rent/check out or buy one of these from the usual auto parts stores for next to nothing - purchase price is only about 10 bucks. They only last for 2-3-4 brake jobs, but for personal use, it's a good deal. Note: when you retract the pistons, brake fluid will be pushed back into the reservoir. It could over flow. Brake fluid is corrosive to paint. Since you will want to remove the lid of the reservoir to allow for the change in fluid level (should be o.k. unless you have added fluid), there is a risk of overflow. If you've added fluid or if in doubt, put rags or a towel or something around the reservoir to catch the overflow so it will not get on paint or other things near by. Once you've done a pad change and see how easy it is, you'll never again want to pay someone to do this.
You have to completely remove the calipers and backing plates, etc. to change out the rotors. I've not done this on a MS3, but the procedure is generally the same on most cars. You will have to follow the instructions as to the pins, clips and/or shielding to remove to get the rotors off, and may need a heavy rubber mallett to get the rotors to "let go" so you can pull them off. I just got through doing this on one of my other vehicles and found having the big rubber mallet very helpful.