The Powerforumstore was very reasonable with my shipping, I have no reason to believe that yours will be any different, they use Triton Express, and they are competent and reasonably priced.
Steve will usually recommend an installer, the installer usually gives a quote after a site visit, It's not something that you want to thumbsuck, every install is different, apart from amount of panels, it depends on distances, and whether the home needs to split the DB or not, also whether the current home's wiring is up to snuff or not. Lots of variables.
Steve will also ensure that the wiring and breakers quoted on can be re-used when you decide to expand (obviously to the best of his ability). It makes expansion easy when you order another 4-10 panel 2 months later, you don't have to redo cabling and breakers.
The upside of getting a installer recommendation from Steve is that he is in the know on how all of the installers perform, he knows exactly what their latest install was like, if there were any complaints he would be the first to know.
But you don;t have to go with his recommendation, you can choose whomever you want.
List of accredited Sunsynk installers here:
https://www.sunsynk.org/approved-installers-1
There are pages and pages of them.