turn signal handle on column

That's part of the whole combination switch and the whole thing will have to be replaced.

Can I replace it myself?

I don't know what you experience level is but it's not a difficult job. It's just a little dangerous working around the airbag.

I'm trying to get the outer plastic shroud on the steering wheel off, but can't get the lever that raises and lowers the column off. How does that lever come off?

It threads out. Grab it at the base to channelocks but it's going to get scratched.