I use programs like HeidiSQL when working in WoW SQL/DB stuff. Other people have different preferences depending on what they need it for, however.
I don't have any tutorials to provide, maybe someone else could help there, as I don't typically work on SQL stuff.
The easy fixes are NPCs missing, dialogues missing, etc, which I believe you can learn to fix yourself by looking up stuff like "How to add custom dialogue to NPC's" or something along those lines, then copying the SQL query you made and post it.
That's just simple stuff though, could be slightly different as again, I don't typically make SQL fixes - although I may actually be doing this a bit more often soon due to a personal project, so I might be able to help in the future.
Good luck to you though, hopefully someone has a better idea of how to get you started.