So, I went looking for a solution for this recently and it took WAY too long to find a working result.
To save others the same time in the future here it is:
panel = ghenv.Component.Params.Input[2].Sources[0]
if panel.NickName != name:
panel.NickName = name
panel.UserText = new_value
panel.ExpireSolution(True)
the Input[2] selects which of the component inputs you are looking at, Source[0] selects the first (only) panel.
Cheers,
DK