The key can be replaced but it's the bubble membrane underneath that has failed.
Have the keyboard replaced and use a external wired or wireless keyboard/mouse to place the wear and tear on external/replaceable devices instead.
The 17" is no longer carried by Apple now, so your downsizing the next hardware turnover cycle.
I have found some inexpensive replacement keyboards on eBay. A few questions:
Are all of the keyboards in the Core 2 Duo MacBook Pro series interchangeable between models and sizes?
Will this keyboard pulled from a 15" model work with my 17" model?
Here is an example: