Thanks!
The names are in the files...the single function one is to be named Change_Font.php and the multiple function one Change_All_2.php
You put them, like all shop items, in the "Sources/shop/items/ " directory. And use them in the same way as any other shop item. Obviously it would be wise for you to charge more for items that do more but that is for you to set up when arranging the handling of them via the shop admin screens.
I have now made a further item that extends the functions of the Change_All_2.php by adding control over borders (a rather large selection of different borders)...the file is too big to post here and I can't add it as a zip file because this forum has attachments disabled. If you want it PM me...I may well make a fourth file giving the borders control as a single function. The new file is to be called Change_All_3.php