I wouldn't want to assemble or do bike maintenance with a multitool. That is unless I felt like pissing myself off that day.
If you wanted a do it all toolkit, something like
this would be more appropriate.
But if you are the least bit handy, you may likely have a number of the tools you already need. I built up my set of tools over the years. There are a number of "standard" tools necessary, such as pliers, hex wrenches, screwdrivers, that you already own. Then there are the specific tools like BB tools etc that you can buy as you need them
For basic assembly of a boxed bike, I would think you can get away with a good set of hex wrenches, screwdriver and some pliers, and maybe an adjustable wrench.
As for howtos. There are plenty of websites with extensive materials on how to do various bike maintenance tasks. I would be wary of whether the DVD included is worth much.
Tire levers are changing tires. You can use a screwdriver...if you want to dent up your rims.
-D