I have no idea what I’m doing when it comes to bikes, I currently have an infinity from costco, is this good?

This is the lowest spec of bike that Trek makes so it may not be much spec improvement over a Costco infinity bike however you can expect better quality control. The main reason to get this would be an improvement in fit and ergonomics, which is very personal, so by all means see if you can test ride it and like the body position and geometry. Costco bikes are typically ‘one size fits all’ which is nonsense. This is listed as a 15″ frame which would be for around 5′ to 5’4 tall