There are three different 14z models (1470, 5423 and N411z) -- they all take standard 2.5" drives, so you can replace the hard drive with an SSD  -- no problem there.

Some will take the older mSATA format of card-style drive as well.

None of them will take the newer NGFF/M.2 card style SSDs.  

SSDs range from well under $100 for a small capacity drive to thousands for high-capacity drives.  A good practical minimum is 256G, which should cost in the $90-100 range;  512, in the $150-200 range.

Thank you VERY MUCH!! I have the Inspiron 14z 5423 Ultrabook, I heard on Leo Laporte's "The Tech Guy" show that SSD drives will boot much faster than spin drives. Is that true or is that not true when an SSD drive is installed in an older laptop?

There was no answer to the above question that I could find. Sorry.