Sliding door noise insulation > cost and best options?

Hi all,

Our bedroom has a fairly standard size (roughly 2m x 2m) aluminium sliding door. Unfortunately, it's single glazing so it lets in a fair bit of noise from the nearby road as well as the odd plane. As such, I'm looking to upgrade to a double-glazed solution. Does anybody know what my options are and how effective they would be? is it easier / more cost effective to just swap out the window for double glazing, or should I replace the whole thing with a uPVC framed door?