Hi Jon! Contact Action is SPST snap-action, close-on-rise. Please see page 2 of the following document for installation instructions: https://s3.amazonaws.com/s3.supplyhouse.com/product_files/White%20Rodgers%20-%203046-5%20-%20Install%20Instructions.pdf
Yes, 3046-5 is the direct cross of 3046-1. You can use this as a replacement.
You do not need to replace the whole unit, but if you would like to, we recommend a V800 series with a reg. thermocouple.