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I currently have my 188 up for sale. I love playing this horn with the only set back being the levers (or paddles) for the valves. With the way I hold the horn and the curve of the levers, I have to force my right wrist to bend down. This is currently causing me pain, even after not playing that horn for a month now. I've tried holding the horn different but it feels too strange to me. I'm selling it in order to purchase a tuba with a more friendly valve set.

But is there another option? Could I have the levers changed or replaced? What would it do to the value if I ever have to sell it down the road? Or am I better off just selling it?

I have often wondered what kind of hand the manufacturers of those tubas had in mind. (It surely isn't a human hand.)
Any good repair person should be able to lengthen the first-valve spatula to make it right for you. I am not a "good repairman" but as a shade-tree tuba mechanic I have done that a couple of times on Cervenys. I used a propane torch to heat the spatula to red-hot, melting the silver solder that held it on.
Then I re-positioned it and soldered it back on with a little inconspicuous reinforcement on the under side. It cleaned up nicely with some fine steel wool and never gave me any trouble.