For rear shocks, he meant you'll want longer ones, otherwise you'll have your 2" lift but no increased downtravel. Crown Vic shocks are popular replacements. It's not something that you absolutely need to do when you put the spacers in, but since you're there anyway, you might as well.
You have struts in the front, which are basically reinforced shock absorbers. Look like shocks, act like shocks, but are struts that, unlike shocks, actually hold stuff together. What you'll be flipping is the strut mount, what the strut bolts to at the top.
You technically have four axles on the truck: Two half-shafts with CV joints (for your independent front suspension, or IFS) in the front, and two half-shafts in the rear, which are inside the solid axle housing and run from each wheel to the differential.
Unless you are breaking your axles, there's no need to replace them.
