Dixiechunk, they make a single whole plate which is the best for straight stitching and also the wider rectangular type plate for your embroidery. You will find that many of the stitches have to be used on the wider plate or they will hit the single hole plate and not work sometimes breaking your needle or at the very least ruining it. I use the single whole for my piecing and a some of my other stitching but the wider hole plate for the fancier ones. I am not at my machine but there is a button to push that will tell you what foot, give you options for stitch width and length and I believe which embroidery plate. Did you get a book with your machine? If so, it will also tell you which plate you should be using plus the other options you have. Also, if you don't use the single hole plate for straight stitching your fabric may get caught up within the wider whole plate and you won't enjoy trying to get it out.
You can check on Ebay for many parts for the 7570. Personally I only use Pfaff parts and not others designed for working on various machines. There are many excellent sellers with original 7570 parts.
Congratulations on your new machine....I love mine and have had since 1998 and it is a workhorse, sews like a dream and also embroiders like a dream although it is considered ancient in today's embroidery machines. I would never ever consider getting rid of this fabulous machine.