Hi JLAR2107,
While LSAT LR and GMAT CR have a lot in common, without an Official LSAT score (to use as a comparison), it's tough to say how well you've developed your CR skills. Did you take any FULL-LENGTH practice LSATs? How did you score on those Tests?
Finishing any section of the GMAT significantly early is usually NOT a good sign. With an extra 5-10 minutes, you could easily pick up a number of points by doing more work, fixing little mistakes, etc. Reading prompts carefully (AND taking the proper notes) is an essential part of dealing with the entire GMAT (not just CR prompts), so the answer to your immediate question is YES, you should read more carefully (it doesn't take that much longer than what you're already doing).
1) How long have you been studying?
2) What resources have you been using?
3) How have you been scoring on your CATs (including the Quant and Verbal Scaled Scores?
GMAT assassins aren't born, they're made,
Rich