Definitely a DIY if you have a little covering experience! The only issues are:
1) make sure you keep seam in the right line
2) gluing on the ends (I just use contact cement) is a little hard where you have to pull & tug as you place and make tight bends
3) Replacement foam is self stick, just be careful you trim correctly so you don't have a big gap of "un-foamed" area
4) Use, or don't, the replacement cardboard. My choice is to glue top & bottom to rest w/o the cardboard, watch seam as you do it
5) Stretch & pull the whole time.