Depends on the size/length of the crack. Sounds like it may be minor. If so, after removing the tap set, I would drill a small hole-maybe one eighth inch-at the end of the crack so that it won't run anymore; "vee" out along the crack with a Dremel or v-file; fill the crack with epoxy; sand smooth with 220 grit or finer after epoxy sets.
Replacing the shower surround could be a big job involving more than just the surround.......damage to walls, new taps, modify water lines, etc.
In my mind, and without seeing it, I would go with the repair unless you have the aptitude/ability to replace it yourself.
Good side is that it won't leak, bad side might be that the colours may not match.........
Hope this helps...........
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