Hey Al! Thanks for the message. The Relief Shading SHOULD work out that far. This link shows the map of where Relief Shading is available and then give you some more information about it. https://www.navionics.com/usa/charts/features/relief-shading
As for the chip, you shouldn't have to buy a new one. All you have to do is renew and then update the chip you have. Stick it in your computer, it should tell you your subscription is expired and then let you renew it for $99, which is way cheaper than what you're going to pay for a new one. When you renew it, you can update it. Make sure to check the box next to Relief Shading so you get that layer.