The other day I was cleaning my engine and notice some oil around the valve cover bolts. So I order a few of them grommets to replace the leaking ones until I had the time to replace the valve gaskets. Well I loosen one of the screws, which had felt that it wasn't very tight, and put a new grommet. Then I put the bolt back in and started tightening when I notice it never got tight or didn't stop spinning. I had stopped there because I didnt want to find out how many other bolts were like this.
What can I do to fix this bolt or any others that I might find?
You want to know how to fix the bolt?? The steel bolt is not the primary problem. Step away from the M5 engine bay.
If you are not familiar with the common methods used to repair stripped aluminum threads, then you should not be attempting that sort of mechanical vehicle repair. Such repairs take high level of skill and experience. Folks who are actually capable of doing that stuff in their backyard learned hoew to do it on a $25 lawn mower or $150 motorcycle when they were 15 yo. They likely screwed up a bunch of times before mastering these skills.
Screws holding such hardware on are incredibly easy to overtighten and strip. Two fingers on a wrench can apply excessive torque and strip threads. Substantial experience or special torque tools are the only things that can prevent damage & you seemingly have neither.
Rather than destroying your car, I would strongly suggest you take it to an indy for repair. Honestly, a BMW is not a suitable test bed for training, experimenting &/or learning Mechanics 101. You need to learn on a $300 Mustang or something, so you can replace the cylinder head for $75 if you screw up. A replacement cylinder head for your M5 will cost 100x ($7500) installed, no exaggeration. You are heading down that path with wreckless abandon.
Unless you are a mechanical wizard with years of auto and/or motorcycle repair under your belt, you should buy an affordable, low maintenance, reliable car that you can afford to have someone else repair. A BMW M5 is not for learning repair, aside from routine maintenance like oil change, brakes or wipers...fiddling will be disasterous from a financial & downtime perspective. There are several good solutions for repairing this stripped thread issue, but none are for newbies. Such a professional repair will likely cost under $100 and it's worth it. Invest your time investigating and searching for the best indy in town to handle your repairs, instead of butchering your car. You will see better results at less cost.
You're playing with fire and gonna get burnt. Sorry for being honest.