I did both of mine on my 2007 E-450. Had a few minor problems but nothing that wasn't able to overcome. Hellwig has their act together and the instructions were good. Rates right up there with with new shocks. You will like the change in handling. Got mine from
sdtrucksprings.com as they had best price.
In full disclosure I did call factory when I couldn't figure out something on the front one. As we were talking the light bulb came on. I really felt stupid but we both got a laugh out of it.
Took better part of day but that included long lunch and a few beer breaks, and the factory call. LOL