MN titles the trailer but not the boat. You'll need a bill of sale to get title if state you are buying from doesn't title the trailer. Bill of sale will also apply for the boat.
Advice on trailer trailers is very sound! I bought a boat in LA, hauled it back to MN and ~150 miles form home 1st tire blew. Another 50 miles 2nd tire blew. Tires looked great and had seller have bearings repacked before trailering... should have had tires done as well.
I've bought lots of motorcycles out of state (and had them shipped) and a boat from LA. As others have said I've found that talking to the seller you can learn a lot.
Pictures are super helpful as are trying to track down others that you might know in the area that can take a look for you. Certain states offer boat surveyors who can do a technical assessment of a boat for you. Similarly you can ask the seller to take the boat into the local dealer to have them do a compression check/ leak down check as well as anything else you'd like - all at your own expense.
Having said all of this only you know you and your degree of anal-ness. If you buy not seeing it in person and see something post delivery how are you going to feel? If you will have a stomach dropping feeling, then you better look at in person for yourself. If you are a roll with a type of guy knowing that so long as it's mechanically sound and if the seller missed showing/ telling you about a minor bump or bruise - you'll be good!
Looks like you have some pretty solid feedback from others that have seen and skied behind this boat, in your other thread. So seems like it's a matter of figuring out how to get it paid for and shipping it. Wire transferring the funds is going to be the best way to make the payment if you aren't doing it in person for the amount it's selling for. You can sequence the wire transfer to tie in with the shipping picking it up. Talk with the seller, get on the same page, you want the seller to be comfortable with the payment as well.
I like to sell something like I'm the buyer and be as up front as I can but people see/ react to different things that may or may not be a big deal to others.