You'll find about a 50/50 split on debanning rifles like this as far as how value is affected. Personally, I think a deban done properly brings the value up since that's what most would want to do anyway. It's kind of like Saiga conversions though. A lot of people think they have the ability to do it well and end up making a mess.
Though with something as uncommon as the SA-93, it's worth sending off if you aren't well versed in modifying AK's. I'll tell you, it is a damn big job. It's simple in theory, but getting the lower tang slot cut is a multi-hour task if you don't have access to specialty stuff like a broach or at the very least a mill with a lot of Z axis. I would not do it again. Mine came out great, but I was very, very meticulous in measuring and laying everything out. My hands were sore the next day from filing.
Here's my slot after I was through with the brunt of the work. I cleaned up the edges a little more, but as you can see, it's a lot of material to remove. Also, the receivers don't appear to be uniformly hard, so you'll get areas that are way more difficult to get through.