The answer to the second question may depend on 2 things. 1. Will you be applying to law school before or after you graduate? If it is after you graduate, then yes, you should send LSAC an updated version. If you're applying prior to graduation then, it goes to question 2. 2. Will the school(s) you're applying to accept the final official transcript directly from your school or must it come from LSAC? You will have to find that out from the school's website or admissions department. I would lean very heavily toward them wanting it from LSAC though because LSAC goes through your credits and adjusts your GPA.
If this question is about money, they will want the final transcript for sure and I don't think LSAC charges for a second review and report. If it is about time, I don't think that matters much either. LSAC takes longer, but the school will probably accept you before your grades for the final semester come out and just want the final transcript prior to your matriculation in Aug/Sept.