Bikepedia link was useless , no info, at all. 2nd picture has no indication of the condition of the used parts you are actually buying.
You have linked to an External BB type crank-set, Not a Square taper one, you need installation tools for the external thread
bearing assemblies the cups with the bearings in them, Have to get them in the frame tight and aligned.
Plus you need tools to remove your current square taper crank-set, and they are different from each other ,
so 2 sets of tools need to be bought.
Might be worth while comparing with just buying new parts installed at your LBS and used stuff with 2 sets of tools.
Or taking the Bike and the new stuff to the bike shop and paying them, Generously,
to remove the old one and install the new one, since you are not buying the parts from them.