My best advice is to pull the assembly from your machine so you can work on it at the bench.
Most people say that just cleaning it up and replacing the drops will work wonders.
I haven't done it to my DE Star trek; but, "one of these days"

As Zitt said, pull the assembly. Flip the targets down and push the lift bar to push them back up; watch how the assembly works and you’ll see it’s super simple to replace the targets.

And again per Zitt, you’ll definitely want to clean it, especially if someone previously used a lubricant on it.

If memory serves, replacing the targets on the DE assembly just involves removing the target retaining bracket which runs across the lower front(?) and then removing the spring from each target, then they slip right out. I found it handy to have a hooked pick to reinstall the new springs.

I rarely see a step by step guide unless vid1900 did one.
Feel free to create one, im sure someone would need it after you.

Sabre
Since you’ve rebuilt flipper assemblies, this is just as straight forward. I would advise taking lots of pictures of Each step, including a picture of the assembly before removing from the playfield. Make sure the pics are clear enough to see the colors and which lug they go on. Take pics at each step going back together, too.

Before removing the targets, take pics of the assembly with the targets up and down so you have a reference point in case of trouble.

Finally, after a successful job, post your own “How To”.

Good luck