Replacing the front sight on a 1911 is a fairly simple job IF you have the right tool. Brownells 1911 Front Sight Staking Punch
Any half way decent gunsmith should be able to do it. If they have the correct front sight in stock, they should be able to do it while you wait. Only takes a few minutes.
Or it can be a nice little DIY project if you'd rather spend the money on the tool instead of the gunsmith.
You will need to know if your sight has the older narrow tenon or the newer wide tenon. I'm thinking yours will probably be the wide tenon.
Changing rear sights which require machine work is a whole 'nother ball game.