No worries, the master sheet is a little outdated and I will be posting a new one when I make an official tutorial/guideline thing for future helpers (which I will be doing very soon). For now, just use B/W front sprites, since the master sheet for Gen III is mostly that anyways.
Yeah, that's totally fine. Just make sure you only use HG/SS backs, not Platinum, and especially not D/P. You could easily get the HG/SS backs from the veekun website.