Hi Norton,
Neoprean wristseals should stop any water running up your sleeves just be sure that they are not that tight as to make you feel uncomfortable, Im sure if you are planning to buy your suit from a shop they will advise you. As for the crate and access on the water it is case of being able to twisrt around to get to it or once you have enough confidence to sit side saddle on your Yak you can access that way. It is worth having a play in water that you can stand in with your Yak so you can practice moving around, sitting side saddle, sliding up to the bow to gain access to your front hatch and taking off and putting on the hatch, rocking your Yak so you get to know what point she will finally tip over at and getting back on your Yak once you are in the water. That way you will get to know your own abilities and the Yaks.
Have fun and be safe
ChrisW