The MS3 is a very good autocross car, you will have a awesome time and really get to learn your car.
Remember to look a head, you should be looking 3 or 4 cones in front of you.
No sudden jerks of the wheel, try and keep it nice and smooth.
Keep your hands at 10 and 2, do not cross over your arms when turning, shuffle the wheel.
a new motor mount or the inserts would be a really good idea especially if your going to autocross, Cant go wrong with the upgraded SRI either.
Also do not be afraid to ask questions and even let someone else drive your car, When people run a better time then I can I know my car has more potential in the form that it is.