VORTIME
The fact that you have a CPL/ME/IR with only 250hours of flight time indicates that to date almost all your flying has been training and most of it probably quite recently. This will give you quite an advantage over someone who has spent the last few years building time to reach 1000/15000 hours without doing any extra training.
That said it will still be difficult, your first jet always is, so here are a few pointers:
1. Good preparation is vital if you can try to read up on the aircraft before you go.
2. If you haven't flown for a while it is worth getting back up to speed before you go (either with a light twin or even a generic jet sim).
3. On the course don't get burnt out. A lot of information will be thrown at you in a very short space of time. You won't be able to remember it all so try to remember the important bits and just get an understanding of the rest.
4. The quickest way to fail a checkride is to not know your memory items or basic limitations. If you can get hold of a list of these and learn them before you go you will help yourself enormously.
5. When in the air (or sim) don't forget your basic airmanship, it was taught to you for a good reason.
6. Finally some of the other students on the course with more hours than you may try to tell you that your wasting your time trying to get a type rating with your level of experience. Just ignore them there are lots of people who pass type ratings with your level of experience (most in fact).
Good luck and don't forget to have fun
TFE731