RE: Deleting certain customers
Excel-users may have old version or without last service pack, so when they did a filter 1 and 4, then select all filtered strings, they may delete all strings between 1 and 4, i.e. also 2 and 3.
To avoid it, use Alt+ for selection or add Select Visible Cells on Excel ribbon.
But better way is sorting, not filtering.
Configuration package will delete ALL records, then create new record - so here you should be careful also, especially if exists validation logics on the fields.
3rd way is using of additional extension, for example I have Record Deletion tool from Ukrainian Localization. Its not so optimal for your case, I hope Edit in Excel is enough for it.