Andersen Lower Replacement Wheels installation

Hello,  I am looking to replace my lower screen door wheels and was about to order Product Code 84-078.  On your website for this item I saw the install instruction for replacing the "upper" screen door wheels.  I want to confirm that this product code is for the lower screen door wheels and also ask if you have installation instructions for the lower wheels or if the process is the same as go the instructions for the upper wheels??  It also appears that the 2 wheels are not clipped into the frame and have fallen inside the hallow door panel at the bottom and is not coming out if I manuver the wheel near the opening to remove it.  
I just read some of the other posts and saw other have discovered their door was upside down.  I'm starting to believe mine might be also.  I purchased the house a few years ago and it may have been put in upside down by the previous owner??  I also saw from another post that I will most likely have to flip the door over to correct it from being upside down??
With that all said, if I flip the door around and install the new upper wheels in the "UPPER" end of the screen door, should I not waste time trying to get the old wheels out of the door??......lol.  thanks in advance for your advice and help.