Yes you could damage either the VCR or the tape or both, If you are not sure of what you are doing the best way is to not do it, VCR is more complicated than an audio cassette player for misaligned tapes, don't treat it as one.

I beg to differ on this department, you do nothing, you get nothing (as far as bad tracking tapes). You can work by 1/4 turns on the guides (assuming bad pictures / hifi sound).
Just keep the count on each guide , take photos/make marks so you go back to the right position once finished

Be careful when suggesting tasks that requires skills to a certain minimum level, I got blamed before for other people's screwups, Not suggesting the OP here is one of them, But from there on I had to caution about the possible outcome in case they are not successful in going such adventures.

I'm uninsured, i decline all responsability actually i might sue him if it comes down to it ;):D

- That technician is an idiot. Never give him a VCR ever again.
- Or he's trying to scare you. Never give him a VCR ever again, he cannot be trusted.

Now, there is truth to "never adjust VCR guides", but then you'd also have to be an idiot. Don't start cranking screws like you're taking parts off a car. We've seen some massively stupid stuff done to VCRs in more recent years, even from drive-by members of this site. Don't be "that guy".

VCR tolerances are very tiny, and even a 1mm turn can have massive effects.

Be gentle, like you're holding a newborn kitten. Not a hamfisted brute that smacks his own hand with a hammer.

No, too much. Most have cross marks (not quite Philips head) dividing the screw in quarters. Never go more than 1/3rd of the quarter. Now, you may turn it 3+ times, but then again you may not. If you turn 1/4th, you may miss correct tracking.

Remember, you're doing this without a scope. It can be hard to unring the bell if you just start twirling and twisting without thinking.

The rule of thumb is go few degrees (5-10) at a time and wait for the adjustment to take effect and so on and so forth, 1/4 turn may start curling the edge of the tape already. It's a lot easier with the scope since it shows you both ends of the waveform of the exit and entry guides, You maximize one end and you move on the the other end, pretty simple. With a TV you have to go back and forth between the exit and entry guides to find the sweet spot.

Yes, I was going to write that -- avoid tape "feathering" (jargon term). Curling, edge crinkles. Damage tapes.

Yes, good call, I forgot to mention that. This is done while playing, and it needs 10-60 seconds to be fully evident if the correction worked.

But I also need to mention this: scopes may not help anyway, if the goal is to "break" (misalign) the VCR to match the misaligned tape. It's not supposed to scope perfectly, in that exact situation.

If refurb'ing a VCR, then obviously, you want perfect. But still noting scopes are still not 100% perfect, there is wiggle room. Lots of factors here. You have to just do it dozens of times, to understand what I mean here.