Channel balance and shash guide

Thanks for your photos. Based on what I see here, you have either our S380-31 or S385-31, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

As for the top sash guide, I am confident that our 18-124P is what you want.

Comparison of the S380 and S385 balance shoes.

Great! That sounds like a good plan. As for whether all your window balances need to be replaced, I think that's going to be a likely scenario. Assuming that they were all installed at the same time, then the window you're having problems with now may be a precursor to more problems to come. It may not be for a few years, but you will probably have to replace those balances eventually.