Installing window channels soon - Advice?

[chevymotocross]

I'm going to be installing new window channels and rubber wipers soon on both driver and passenger windows. It's an 87 silverado which has power windows. While I'm doing the installations, I'd like to address why both windows are slow to go up/down. Is this just a matter or lubricating the window mechanism or should I just go ahead and install new motors? Any tips on easy installations of the window channels and wipers would be greatly appreciated. I am not touching the vent windows.