Where can I get glass shards smoothed out?

You just need to borrow someone's dremel moto-tool. If the shard is not too small or too fragile, you can put a tiny diamond infused drum bit on the end of the tool and sand the sharp bits. I used to work with stone and I also tumbled glass, and tumbled glass becomes frosted and you have to be careful with the tumbler you use. The tumbler bowls are very specific as to grit, and if you put the wrong grit, such as coarse, into the third tumbler bowl it will ruin your piece.