With most TAs, your reservation is thru
DCL, no matter who books it. The only exception is that there are agents who buy up a block of cabins and then resell them to the public.
Provided that your payments are to DCL rather than to an agent, you have nothing to worry about. If you have a concern, you can always book the ressie yourself thru DCL (making your deposit with them) and then transfer the ressie to the TA. You are then assured that you went thru DCL--and they're not going out of business!
Now....I'm not sure that I'd work without a TA who is a DCL specialist on my first ever cruise. And be careful--all agents claim to "do Disney" but some of them are as dumb as a box of rocks, and I just insulted the rocks. There are a lot of options. There is a lot of good information here.
I'm not sure from your post if you've already made your ressie. In that case, you are finished and there is no downside to transferring the ressie. If you have not made it.....DCL would love to sell you one of their "all inclusive" packages. That means 7 days, whether as land/sea or as a 7 day cruise, and would include transfers and insurance. No doubt, this is the easiest way to book things. However, depending on the season, your choice of resorts, number of people, etc. it may well not be the most economical.
If you are doing a 7 day cruise without Disney World, your only real questions are whether you want transfers thru DCL (if you are flying in), whether you want your air thru DCL, and whether you want insurance thru DCL. Your options include private limo or rental car, booking air yourself, and private insurance or no insurance. There are advantages and disadvantages to each option.
If you are booking a land/sea, there are MANY more things to consider. Each ship cabin is tied to a resort category at WDW. You may want a higher or lower resort than your cabin allows....you may want another type of pass to the parks, etc. Again, each choice has a price tag.
So...for a first timer, a good TA is a huge help. You can get good info here...you can go crazy considering all your options.....have fun!