My problem is that I alredy have made hairs & rigged the mesh, but now I realized that I wana still fix some stuff in mesh. Is there any way how I can fix mesh without disturbing hair?
I hope someone will read this & give at least some answer…
appyling the hair particle system modifier should do the trick 
If your using 2.5 there’s a nice “disconnect hair” feature. Click that, edit your mesh and then “re-connect hair”
I am so very pleased to hear that!!! Excellent improvement on the hair systems.