Vostro 3460 Hard drive issue

I am a tech myself.I just bought 4-5 of  Vostro 3460 Laptops.It all works fine except one of them is DOA.It will not boot up upon arrival.

It give you a message : no operating system found.

I called Tech support and talked to their first level support person.She asked me to go into bios and change Sata mode from Intel Smart Responce to ACHI and

inserted Dell OS to load windows.When it finished.The laptop booted up and She said I could changed Sata mode back to Intel Smart mode.However,after I changed it,the laptop gave me no operating error again.She then told me that I need to format SST hard drive (32 GB) which is bundled in the system.But I will have to stay in AHCI mode.otherwise the laptop will not booted up.Also,she mentioned to me that she can have tech to install factory software installed hard drive to trade my not bootable hard drive.

My Question is

1)If I replace default 500 gb hd to 1TB hard drive,How do I install windows and dell drivers and software in correct Sata mode-which is Intel Smart Mode.

So far,If I load Dell windows cd in that mode,it will tell me that I do not have hard drive.I guess it need 3rd  party drivers.

2)If I changed Sata mode to Ahci,How do I utilize 32 gb solida hard drive for cache.It will not work in that way?

Thanks you so much.