With the RHCE, you have the advantage that this is a performance-based test...not multiple choice. If you can get the job done right, you can pass. This isn't just a memorization exercise. I'd take a look at the list of the topics covered by the exam here http://www.redhat.com/certification/rhce/prep_guide/ and make sure you can can build and troubleshoot each item listed. I wouldn't skip anything because you did it a year ago and think you remember.

Also, I don't think the RHCE is as hard as it once was. If you've read the war stories about the folks struggling through the exam and barely passing or not passing at all, you're probably reading about someone who didn't understand all of the technologies on the list like they should have or (maybe more likely) someone who took the exam a few years ago. I was RHCT certified and went to the 1-week training with the exam at the end and passed without any issues at all. If you have the money, this might be the way to go especially if the certification is important for you to have.

Good luck,