Replacement coils springs and shoes

Hi, I'm looking to replace some snapped coil springs on 20 year old U.S. Window Factory windows. I removed a spring and shoe from the working side on one of the broken windows to take photos. Please provide replacement part suggestions. Right now I need 10 sets of shoes and coils for this size window. Some of the smaller windows need replacements also but I'll remove and send photos of those windows once I have these done. Two questions:

1) while the very top of the tracks have a removable cover that reveals an opening wide enough to remove the spring and shoe, every window has a screw right in the middle of the track that blocks the shoe and spring from sliding up to the top of the track. The screw is slotted and can be backed out but not easily removed, so I cut the track at the location where the spring was mounted to allow me to remove the spring, cover and shoe. My question is, I'm not thrilled with cutting the track, but it seems a fairly common way to remove the parts, is there a better way?

2) for general maintenance, what do you recommend to lubricate the tracks and shoes?

Thanks, Bob