Yes, if you're a dual-fuel customer, both meters will need to be replaced. Your supplier will aim to install both meters on the same visit to make things as easy as possible. You will only need one in-home display to view both your gas and electricity usage. If your gas and electricity accounts are with different suppliers, you will have two separate smart meter installations - one from each of your suppliers.
If your home’s gas and electricity are supplied by different suppliers, we suggest having your electric smart meter installed before your gas smart meter. We have a lot more information about smart meters and the installation process on our installation process page.