In the world of dealing with other peoples drawings and many times ifs from the same people. I recommend working with the Translate Layer command
Ribbon: Tools tab Standards panel Layer Translator
Menu: Tools CAD Standards Layer Translator
Toolbar: CAD Standards
Command entry: laytrans
In the Layer Translator, you specify the layers in the current drawing that you want to translate, and the layers to translate them to.
Specifies the layers to be translated in the current drawing. You can specify layers by selecting layers in the Translate From list or by supplying a selection filter.
also note and experiment with “Filter” and save when done so you can load them back for another project that needs cleaning. Have fun, its worth the time