Caroline,
Here's what I see about your machine, it's controls are very similar to mine:
A: White nob with blue ring and designs on it on the left is your stitch regulator.
B: Put it on any of the darker filled in patterns, then put the stitch width nob on 0 to 1 and you will get that pattern. Any farther on the width nob decreases the pattern. At "5" all you get is a satin type stitch.
C: For the lighter patterns on the nob, you'll need to move the pointy up lever to the left to engage reverse. These patterns cause the machine to run backwards while making the stitches.
D: The bottom white nob with the small chrome ring around it is your stitch length regulator. To get the tightest patterns set it on 1/2 to 1.
E: To get straight stitch with the needle centered; put the needle position on "M", the stitch width nob on "0" and the pattern control nob on "manual".
F: To get zig-zag without using the patterns on the pattern nob, set the pattern nob on "manual" and move the stitch width control anywhere right from "0". The higher the number the wider the stitch.
I find it's best to leave the needle parked in the center position unless you need to move it for a special pattern.
Let me know if these instructions help any. I haven't gotten "totally" familiar with mine but I'm getting there.
Now, where are you getting your new cord block and motor? Just curious.
Joe