Crowley's Yacht Yard did ours. They let me stay at their working dock for a few days while I prepped everything. When they pulled the mast, I couldn't believe how fast and efficient they were. Call ahead, they get busy.
Cost to ship our mast was going to be $3000. We lucked out when we heard of a group of 7 boats all shipping masts together. We jumped on that one! Saved a bundle. Found them on the AGLCA website.
Crowleys put my mast in their storage bldg where I could prep it. If you truck it, pad everything WELL! Dirt, road grime, diesel soot, gravel, everything will attack it.
You can carry the mast on board but I would not extend more than 10' over the bow and stern, and I think that is a bit much. Maybe 10' bow and 5' stern. If your mast is longer...
Our biggest issue was finding anchorage spots out of the channels. Do your homework and have guide books along. Internet will be spotty.
Check the current status on Hoppies on the Mississippi. They are having shoaling issues. They are the last stop for fuel for 250 miles. If you can't stop there then you'll have a much longer run between fuel stops plus I don't know where you'd stop for the night in place of their 'marina'.
Turner Marine in Mobile is great. Please say hi to Christie and Roger for us.
And last...we LOVED the trip.