Changing HarddriveDisks

Hi all,

after 5 years up without any problems I would like to replace my disks.
At the moment I have the system installed on a 30GB cheap SSD and separated via LMV the App-Data to my HDD

As storage is cheaper nowadays I would like to replace the two different disks with one big SSD.

Now my question. How could I achieve this or is this not possible?

And the other question would be, how could I use the old HDD in this case as a build in Backup?

Thanks in advance