The easiest way is to wheel it with a ramp. If you do not have a ramp (and no one will help you, or you need to do this repeatedly), you will have to lift carefully. I recommend using your back in tandem with your leg muscles to lift--not to the point of straining either (if you are not used to lifting with your back, I suggest using extreme caution and letting the legs do most of the work until your back muscles can be built up). Lifting it from the bottom with the weight close to your body makes the most sense, if only because you are better able to control the machine that way. Needless to say, you must make sure you have good footing before trying this since a fall with such a load will do more damage than improper lifting.
If you are going to do this regularly, I highly recommend building up your abs and back muscles to make it safer. One thing I have found helpful is a Torso Tiger-TM or something similar. Once you use that, you are working the back and all the ab muscles. A pair of Ab Dollies-TM or similar products (if you are handy, you can put casters on a piece of plywood and it will do the same thing). With that, practice the twisting and going side to side with it. If you have two, you could also do other exercises that require two of them. Stay regular with those exercises (it will probably take less than 5 minutes a day). Ultimately, this will use all the ab and back muscles, reducing the risk of some unused muscle getting hurt and wrenching your back. And thus it will make it safer to lift that thing in and out of the truck, since you will be splitting the load between the knees and the back.
Of course, a power lifter will make the job much easier. But those things take space that may not be available (you do need to take it out of the truck when you get to the job), and they depend on electricity that might not be available at the site where you need to remove it. I definitely suggest investing the $20 or so on a nice, sturdy piece of plywood to create a ramp to move that thing (the safest and easiest way).