If your shocks are blown you should replace them anyways - that has nothing to do with auto-crossing or tracking - it has everything to do with road-safe equipment. So, yes, replace those. Just get something such as a set of Bilstein HD struts and shocks. You can re-use your springs or buy lowering springs. It's up to you (i.e. how much money you're willing to spend). Check your bushings and balljoints because you might have to replace those too (and you seriously might have to if they've never been done before - especially considering you've got two blown struts).
The transmission will be fine; just make sure there's enough fluid in there. The suspension doesn't affect it.
One thing I forgot to mention earlier is to make sure you've got at least near 50% of your brake pads left. If you have less than 1/3 life left in them, you should replace them before your auto-cross event. Otherwise, that's it.
Auto-crosses and even track days are NOT rocket science. And the last thing you want to do is to fool yourself into believing they are.
Last edited by Bayerische E46; 02-08-2013 at 09:32 PM.