Your first point is good and points at more that the lens is out of place. I would still clean the spindle when you have the drive apart. Like I said even if it's not a problem now, it will be in time.
You never want to power the machine ON when the DRIVE cover is off. I may have alluded to powering it ON when the UNIT cover was off, but NOT the drive cover. If you do you will see the red laser come on. Whatever you don't look directly at that. I assume it could harm your eyes. I did this once looking from the side and immediately unplugged the machine when I realized what was going on.
Another think to keep in mind. Don't move the machine or drive around when you have the drive cover off(also don't move the drive cover itself around). Their are plastic pieces that can get out of place. If they do you will have a hard time getting the cover back on. Trust me on this one. I once had this happen to me and I somewhat forced the cover on. After I powered the machine ON it made a terrible grinding noise and gave me a u88?(can't remember the code) I quickly unplugged the unit and after a few scary moments(I was thinking I was going to have to take apart one of my other machines to compare the two)I finally figured what I had done wrong.
Long story short just lift the cover off and place away from the machine. Then after your work is done carefully place back on the drive. Their's nothing on the underside of the drive cover that usually needs cleaning. It's hard plastic. The rubber part attached to the main part of the drive is what needs cleaning.
Good luck and I think it's really easier than all these warnings might lead you to believe. I'm just trying to cover all the bases for you and hopefully you can learn from my mistakes