The lawyer sets up the whole storyline for you and basically gets you to meet all the players in Vice City.
You may have finished the storylines, but the way to find out if you've done everything is to check your stats. If you are at less than 100%, then you still have things to do. Once you reach 100% there will be various "rewards"
Here is a link to a gaming forum that has a great VC forum:
Great Vice City Forum
Be aware that there are several spoilers on this and not all of them are clearly identified. There are checklists for 100% completion, guides to finding everything, and lots of easter eggs and other secrets.