Learn me about nib polishing

Can you polish a nib easily with micro lapping sheets like those used on straight razors? If not, what is the best DIY procedure. Is this noob doable? I would only consider doing this on easily and cheaply replaced nibs, such as those for Lamy, TWSBI, etc.

Yes, you can use the Mylar sheets to smooth a nib. Just a caution, though. Most cases of rough or scratchy nibs are due to misalignment, not rough metal. Examine a nib very closely under magnification (10X is good) to make sure that one tine isn't higher than the other. Trying to polish down a misaligned nib can seriously damage it. If you do polish, take it very slow, test often, and don't use anything too coarse. A few strokes on a 12K sheet may be all that's needed.
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Brian Gray of Edison Pens has an excellent online seminar/tutorial on Nib Tuning and Smoothing. It's long, but very thorough and comprehensive.

Less is better. You can't put metal back on the nib. Slow and steady with lots of testing. I also think it's best to work on something softer than a countertop to provide a little "give". That will make a smoother result. I now use micromesh sheets that are foam backed, but with sheets I'd use something like the cardboard back of a notepad.
I'll stress it again, go very slow, I've ruined nibs. If it's a special pen, consider sending it out. Lamy Safari? Go for it, you can buy replacements inexpensively.

I recommend leaving it to the professionals. Seriously ... especially the nice ones.

If you do, you should always disclose that fact when you sell. I've bought a few used pens with massacred nibs.

As mentioned above, I'd only try it on cheap and easily replaced nibs, if at all.