Add class or id to Control Panel block holding custom field type instructions

I’ve successfully created an extension that adds a Custom Field type. I would like the instrutions area of this custom field type to have a new class. I need to be able to target those somehow - probably with a class as I may have more than one type of this field. Here’s what I’m seeing under the hood right now (simplified for legibility):

Let’s say I want to add a class of “crazyLegs” to the instruction area, which I know I can simply do with some jQuery - but there’s no way to target the field, so I would think I’d have to re-write the output of that field block a bit. I’m looking for something simple like this:

<div class='publishRows' >

...

<div class='paddedWrapper crazyLegs' >
<span class='defaultBold'>Instructions: </span>
these are my incredible instructions. I want them formatted in a special way. 
And because of the 'crazyLegs' class, I can now format these in a super special way!

</div>

[field content here]

</div>

Everything works fine in my extension now, but I’d just like to do up the instructions in a certain way for this custom field type. Thanks.