1. While you have it apart might as well do all 4. If 1 split the others aren't to far away. 15 year old rubber!
2.Some have had good luck with them others haven't. When I did mine I used Dormans and they held up great and are a lot cheaper. The Mecha's are a lot "flexier" whi h eases installation.
3. I would drive as little as possible. Split boot introduces dirt/grit and throws all your grease out (dry bearings).
4. The indy kit is complete...comes with all you need. Roward just used this kit a week ago.
5. Nothing...if all goes smooth it will take about 4-5 hours to do both sides. Give yourself a weekend in case you run into issues (rusty bolts).
Good luck