Well, what steps did you finally take? Is there a way you could post a screen shot that shows the gradient and the settings dialog you ended up with?
I'm partly asking because this could help others who want to learn about these tools in Lightroom, and also we could get some insight and maybe helpful suggestions!
Of cours, like I said earlier the "traditional" approach would be, in Photoshop, to use an Adjustment Layer, a mask, and a gradient -- you might want to try that out and compare with what you did in Lightroom and see what is the easiest and best, although I myself am kind of a die-hard for squeezing as much as I can out of Lightroom and this could be a cool experiment for us all
!