Welcome to the forums.
When it come to water damage, what looks like minor damage can actually be major, depends whats hidden. Pictures would help of the water damaged areas, hard to envision. As mentioned you need to get the seems or whatever leaks on the roof sealed using Proflex or Dicor. If it's worse then just normal cracks on the old sealant you may need something else. You said you can reach through to the insulation, does your ceiling come out? You need to dry out the insulation or remove and replace it after fixing the source of the leaks.
If it costs little or nothing to have the pro out to look it over, go ahead. If the fix is costly you my want to run it by the group before you sign on any dotted lines.