Congratulations on your engagement!
Don't panic, what you are feeling is totally normal. There are so many companies to choose from and every one has a different policy and can benefit you and your guests in different ways.
The most important thing to keep in mind when you are looking for a travel agent is that you trust them and they are responsive and understand you vision. They need to answer you and your guests when you have questions and keep the communication open from the beginning of the process until well after. You'll be working closely with this person for months, if not years on the most important day of your life, if she/he is great, you will practically be best friends by the time it's all over. I don't think it matters whether they are down the street or not. What matters is that they will alleviate all your stress and do their job well!
You have plenty of options and each company will assist you in different ways. Some companies work soley on weddings and are likely to have amazing relationships with wholesalers and onsite vendors in destination. They will be able to negotiate good group pricing and liaise with the resort wedding coordinators to make sure that your vision is brought to fruition. Other companies will sell all types of travel and have a designated wedding or group person.
Make sure you do some research and if you find someone that gives you a good gut feeling- stick with them!
-Blue Petal Destination Weddings