What should the last week of training consist of?
The answer to this question depends on a variety of factors. Such as:
1) Your approach to the race. Is it a tune-up for a bigger race later in the year? Is it your key race for the year?
2) The amount of training you have done up to this point.
3) The length of the race you are doing.
In general, though it is best to "taper" for a race. This may mean a 30-50% reduction in the amount of training you have been doing. Also, most of the training should be relaxed and seem easy except for a few, short intervals to help simulate race pace.
One thing you may want to do is find yourself a coach that will be able to give you a much more detailed answer based on your specific situation. You can either find someone in your area or online.
That all depends on your average training load and the race distance you are competing at. A general rule of thumb is to cut back the volume of training to 30% of your high 3-4 weeks prior to race week. Do a few race pace short workouts to stay sharp in each discipline, practice your transitions, and add a few rest days. Listen to your body.