2001 GM LS-C 2 questions/Ethanol & power on passenger side

[MrRealtor]

Hello all. I purchased this GM about a year ago. It had been sitting about 6 months as the owner died and the family just left it until I saw it in the driveway and bought it. I understand he may have used Ethanol which I was told was a bad thing in this car. I only use real gas but have replaced many items in the last year that are fuel related. Could the use of Ethanol be the cause of failure? In general I would like your opinion.

Also, I noticed on the passenger side both the window and passenger seat move slower than the drivers side and if someone with a little girth is in the passenger seat, it won't move at all. Any ideas?

PS: I wanted to add that I love the car. It runs great (when something isn't wrong) and gets respectable gas mileage and only has 77K miles.