I'm not a member, but have competed in CTR. I say go ahead and do the competition, even if you don't do well you'll have a score that breaks down and shows you what the problems are and where you need to problem-solve. If you do pass/fail you don't get as much detail or a score so you won't be learning nearly as much.
Here are some important things to think of:
1. Don't let your horse eat or move during P&Rs...their pulse will go up (it's ok to let them eat--just not DURING the P&R--but before the vet check it's good because it'll help their gut sounds)
2. Make sure you take the time to let your horse drink...and to sponge water onto them if they won't drink(before P&Rs you should make sure they are drinking and sponge them all over to cool them down as much as you can. Also, if they aren't great about drinking I'd consider electrolytes.
3. I'd wear a stop watch as well as something like a GPS that can measure how far you've gone. This way you can make sure you know how much time you've got left, how much distance you've got left, and what pace you need to keep. This is huge. You want to do the first half faster than the second to allow for unexpected incidents and so that you can walk into the hold/finish instead of rushing in. :)
4. Before competition day make sure your horse is used to having your hands all over him, a stethoscope all over him, his lips pulled up to look at his teeth, etc. You don't want him jumping all over and giving the vet a hissy fit. If he kicks/bites the vet can take a behavior penalty...if he flinches too much he/she may think there is pain going on...pulse may go up if your horse isn't used to the stethoscope, etc.
Hope that was helpful...it's all I can think of at the moment!
A horse is the projection of peoples' views about themselves--strong, powerful, beautiful--and it has the capability of giving us escape from our mundane existance.