It depends on what you want. You're entitled to fair value, or a comparable replacement.
Shop for a used Klein to establish the value, then speak to the manager. OTOH - it might be that fair value is less than $400, and if so, and that Trek is worth that much than you may opt for it, though IMO, you'd want a new $400 bike, not s component swap onto the frame of a bike worth that much.
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