Another possibility is to use a good Super Glue product from Permatex or Loctite. If the insert on the underside of the engine cover is only cracked from the screw being overtightened, you should be able to apply a Super Glue product to the cracked area and just hold it closed for a few minutes. Should be good as new and fully functional. You won't overtighten the screws since you're aware of the problem.

And, oh by the way, it's a common practice for folks (including service techs) to overtighen screwed assemblies that consist of plastic materials. Over the years, I've found cracked plastic assemblies throughout interiors where someone made attempts to repair something and then overtightened when re-assemblying brackets and/or trim panels. Just human nature to turn until we can't turn no more!