I have been driving a V10 SuperDuty since 1998 and can say nothing but great things about them. I can change the oil for about 30 bucks, an annual fuel filter is about 12 bucks and the K&N air filter is easy to clean once a year.
I only put about 10k miles per year so that adds up to about 100 bucks per year for maintenance. That is pretty cheap. I did change the tranny fluid at 30k but that was pretty easy too. I just drained the pan and replaced the external spin on filter. Took about 8 quarts. I am getting close to 50k on my truck now and will flush and fill the cooling system. All in all, pretty easy and cheap to do.
Haven't had a truck long enough to mess with the plugs yet. I'm not looking forward to it, but when / if the time comes I'll just dedicate a Saturday afternoon and get it done.
I am running an aftermarket programmer from 5 Star and the thing is incredible. It removes the factory torque limiting strategy and really wakes up the drive by wire technology. MPG is better too. In mixed driving I can easily get 12-13 and unloaded on the highway I can get 14 if I keep it under 75 mph. It will use some gas when you load it down but for me that is a small percentage of the time. And with the relatively low miles per year I am not spending a fortune on gas.
Every situation is different but unless you put quite a few miles per year, or are towing 90 percent of the time, the diesel will not be a good choice. For me, the breakeven point was way beyond 10 years of ownership. I have never kept a vehicle that long.