IMO, as long as you get all of the rest of the LR coral n critters removed(along with all water you're gonna reuse), then you should be safe. As far as your sand bed, you should be good either way. Pros and cons seems more opinion than too much fact related.I like the DSB for the ability of having those critters that depend on the DSB(gobies, jawfish, etc). Reguardless, you have alot of LR for denitrification and if you do decide on a DSB in the future... you have a refugium. BTW, IMO trash or donate that seeded existing sand bed to your local reef club or trade some with other local reefers. Good luck.
Repto
There's nowhere else I'ld rather be... unless, of course, you're buying