Depending on how badly its damaged, the bad crown can have anything from little noticeable effect on accuracy to a substantial effect, greatly degrading accuracy at longer distances.
If a gunsmith saw enough damage to say it needed work, you probably ought to get it done. Check with your area gunsmiths. It takes special tools and a little know-how. Probably $25 - $50, depending on the smith.
(I can't imagine why a working gunsmith can't do the job himself, unless he just doesn't have the right tools. It may be that his business is focused on long guns, and he doesn't have the right tool.)
And, more importantly, if you bought the gun new, you've got to figure out what you've done to damage the crown.
The most likely cause of damage, is being careless with cleaning rods when cleaning the barrel.
You should always clean the barrrel from the breech (back) end, to avoid damaging the crown with the cleaning rod, and be careful when pulling the tip or jag BACK for another pass.
