I would omit the spring inside the accumulator piston but would install the outer spring if available.

For the band adjuster a 4" Crescent wrench works good, just tighten it snug (no gorilla) and loosen the desired number of turns; it's not that critical. Since you have the pan off you can use a 5/16" or 3/8" Allen wrench as a feeler gauge between the lever and the piston plunger...place the flat sides of the Allen wrench between the lever and plunger and tighten the adjuster until the wrench can be passed between them easily.