Safe Harbor in Haverstraw allows you to DIY, but they are somewhat unreliable & slow (haulout/launch). We won't let them touch our boat (long story), but they let us do all of our own work.
Note on transiting the canal. Our boat neighbor purchased his Contessa in Wisconsin and tried what you're looking to do. It got too shallow & he had to ship the boat the rest of the way. This was 2 years ago. I can get more details if interested.