No problem.
Not ignorance, just 'not knowing'.
Without actually looking, I'd suspect that your Sony does NOT have an M.2 port. Those are pretty new.
So...for a larger SSD.
Yes, you can switch relatively easily.
You have 2 options, either a whole new OS install on the new, larger SSD
or
Migrate from the old 128GB drive to the new larger drive. Either 250GB, or 500GB, or whatever.
Samsung drives come with a migration software, and often include a USB cable to do it with.
Connect the new drive via the included USB cable, run the migration software (hopefully it works OK).
Take the laptop apart and swap the drives.
Boot, and it will probably work.
The one thing you REALLY have to look at is the thickness of the drive you wish to purchase.
All current SSD's are 2.5" format. But possibly slightly different thickness. I believe the Sony Ultrabook relies on a 7mm thick drive, as opposed to the more common 9.5mm thick drive.
http://www.pcworld.idg.com.au/review/sony/vaio_t_series_svt13116fgs_ultrabook/433511/
"It's worth noting that once you remove the battery, you can also remove the access panel, which allows you to access the free memory slot and the SATA drive bay, which accepts 2.5in drives that are up to 7mm thick."
Such is life with an 'ultrabook'. That's how they make them 'thin'.
So...look around for a SATA 3 SSD, in a 7mm thickness. They are ALL 2.5" wide. Just a few are 7mm thick, as opposed to the normal 9.5mm.
For the M.2 possibility...look in the user manual and specs. But I doubt it.