Coil balance spring replacement

Hello. I have vinyl replacement double Hung windows in my house that utilize a coil balance spring. Both springs on one window have broken. I note that you have several types of springs and feel confident that you would have the type I need. However I cannot see how the coil could be replaced. It seems to have been attached to a plastic block which is held in a U-channel with a long screw. Any assistance you can provide would be greatly appreciated. The Manufacturer of the window is unknown to me and the contractor is no longer available. Identifying labels on the window: The Door & Window Place. Mdl:2300 WHT Line: 2 Double Hung Lot: 104,164 Solarban60 AR/KR Top Bin 8 Solarban60 AR/KR Bottom NAMI NFRC 100/200 Code: ACU Rating NFRC Series 2300/2400 DH MST: 3050 ACU-1-8 02-M

Thank you very much Paul. I believe this will do the job.
Order placed.