My tub is a bit old - a Thermospas from around 1999 or 2000 - and I'd like to replace/update some of the jets since they're showing their age. The chrome covers keep falling off, and the plastic underneath is in pretty bad shape (see pics). The problem is I can't seem to find replacements and am truly not sure how to remove the old and put in the new, so any help you can provide would be greatly appreciated. Thank you.