It's up to you. The majority of avid turtle hobbyists refrain from letting any pet turtles go into the wild because they can decimate other turtle populations. What's more, it's not native and can become an invasive species.

Try to look of this forum for all the care you can give a sick hatchling: www.turtleforum.com.

They'll assist you when it comes to sick turtles. Thing is, small res's can rebound. Keep it out of the water for long periods of time, keep it warm, give it sunlight(though not too much.)

More can be said. but I've saved a few this way. It's probably suffering from dirty water and/or lack of proper diet and therefore, soft-shell.