Sorry -- I'm talking the same "middle stone" BDL is. Maybe I should have just said medium. For waterstones that's somewhere in the 1,000 - 2,000 range. I'd have to re-read BDLs oil-stones posts to know which name. But I'll let you do that!
If you use the "magic marker trick", and you check frequently, and you're not using the coarse stone (the one meant for reprofiling), you won't do any damage to your knife beyond some cosmetic scratching. That may be fixable with a rust eraser or some micromesh or some wet/dry sandpaper, later, too. I'm not really expert on this fixing the cosmetics -- I have a stainless knife that responds well to a rust eraser for fixing the cosmetics; tried the same device on my sister's German knife and it really didn't help. So.... I'm sure something else would. But I don't know what grit of wet/dry or what particular micromesh or some other option. I just know had I time to experiment it wouldn't have been difficult.
And maybe this is particular to waterstones -- maybe the Sab stainless isn't too difficult. I have a Japanese stainless knife that is way more of a pain that the Sab carbons, but I've worked on some European stainless and they've been pretty easy. NOT Sab-carbon easy, but close enough. I think just because they're softer steel. And... again... maybe easier on the waterstones.
If you're super worried about preserving cosmetics, then sure use cheaper knives. But really, if you're not using the coarse stone, it's not easy to destroy a knife. Even *with* a coarse stone, if you're using the magic marker and checking a bunch, and not leaning on it like you're doing deep-tissue massage, I think it's still pretty difficult to destroy the knife. You might be able to get it to the point that you need someone else to fix it for you with a coarse stone. But even that would take some doing, or some not checking your work.
I'm not encouraging starting with coarse, just encouraging you to get started.
The issue with both the coarse and the fine stones is keeping a consistent angle as you rub the knife against the rock. A coarse stone will grind away enough metal that you can "mess up", especially if your pressure is bad, your angle is bad, and you don't check enough to correct those things early on. A fine stone will round out the edge you created with the medium. It's also more difficult to keep a consistent angle over more strokes, and you'll need more strokes with a finer stone. So all that balance is what puts you in the middle to practice. Just sticking with a 1000 stone on your stainless Sab will get you to the point (I'm guessing) that it will have a better edge than you're used to in fairly short order. Even if you're not "good". The belt grinder guys you pay $4 for will do worse than you yourself will do, even as a n00b, 90% of the time.
I don't meant to encourage recklessness. Maybe I'm less conservative than my betters in this regard. But seriously, you got a hunk of metal in your hand. You're going to rub it up against something-anything, it's not a thin piece of porcelain. I feared getting started for months, actually, and felt very silly by the time I had a lesson. "So let's see what you've been doing..." I was told as I started. And I was handling the knife like it was a baby metatarsal I needed to reshape before a transplant. "You haven't been doing much, clearly". Right. Hours later, I was still not confident, and certainly not "good". But I got decent edges and wasn't afraid to go at it. The lesson was helpful, but the not-getting-started could have been solved with a magic marker, the advice to check frequently, and the advice to not bear down too hard with the hand atop the stone (which created significantly more wobble than my mild nerve damage did).