Hey Phil,
To removing the bold face of required fields, edit the form you are using, click on "Form Settings", then click on the gear icon in the top-right and choose "Edit Custom CSS". Then paste the following code in that box:
.mktoForm .mktoRequiredField label.mktoLabel{
font-weight: normal;
}
Step-by-step instructions with screenshots to edit the Form CSS can be found here:
https://community.marketo.com/MarketoArticle?id=kA050000000LHXhCAOBest,
Will