Removing Acorn Sliders

I need to replace the roller in my Acorn Dorwal sliding glass door. I will order parts from you as soon as I verify that the old rollers look like your replacements. My question for you is: do I remove the sliding panel first or the fixed panel first? Are there any other important things I need to know in removing them?

Also we have air leakage at the bottom of the doors - do you sell any parts that I can replace while they are out that will help with this issue?

Thanks,

Ron