This advice may be a little late, we did the same thing. Here was my process:
I dumped a lot of ACAD details into a single Revit detail view in a distinct, separate rvt file. In groups 40 or 50 at a time. Then explode them all.
Select all, then filter. You can spot the ACAD styles, and you filter for each line type, wide, thin, etc. and re-assign to revit styles. Delete things like defpoints, and so on.
Then after you've cleaned all the details of the ACAD line styles, do the same with text. Then you have to deal with patterns, those are the hardest to 're-map'. Many of the patterns are best deleted, they really don't translate well, they leave a lot of oddly named pattern styles.
Once all of the objects are set to revit styles that match your revit standards, you cut and paste each detail into a 2nd clean revit file that is to your firms standards, view by view, leaving all the acad junk styles in the first file. You've got to leave all the crap ACAD styles in the intermediate file.
It sounds tedious, but once you get rolling you can do a detail every couple of minutes. If you have already dumped them into individual views, you're stuck. You just can't clean them up as a group, its one by one.
After you get them all cleaned and organized, you can add in revit native detail elements to the ACAD-based details as time goes on. We are re-building a lot of them as we go, but still the old details are a good framework. You have to get from here to there somehow.
