Well as far as working on one before.....never have. The overall mechanics of the 353 is just like any other motor. I have worked on many gas motors and a couple cummins diesels. I feel that the 353 is overall pretty simple to work on. There are a few differences that merit mentioning.....valve train is different as there are 4 exhaust and no intake valves, and the injectors are self priming with no lift pump. To answer your question the motor is easy to work on , but get yourself a manual for all the specifics of the valve train. Setting the rack is the most temperamental part and can be a pain and cause damage if not set right eg. piston damage due to the injectors being set too deep or running too rick or lean in one cylinder. This will cause a melt down of the aluminum piston in a short time ( I mean hours not days of run time). The valves need to be set right. If the exhaust opens at the wrong time funny things like the motor running away with its self happens because it is running backward and pulling through the exhaust. The motors are the overall best diesel on the market as they produce more torque with less RPMs. They are less expensive to repair, and there are plenty of parts available.
So now don't you wish you hadn't asked.
I just jump into the motor and let the chip fall where they may......you learn more that way. Besides there are always phones handy when you get too deep to cry for help.