Hard Drive 0 Error code 2000-0142 on Dell XPS running Windows 7

Hello - This morning when i switched my laptop on i got the following message on a black screen: "operation system not found"

I am a complete novice but i did some research and have managed to access the BIOS to restore factory settings and run the diagnostic tool, which gave me the following error:

Code: 2000-0142

Validation: 87568

Msg: Long self test unsuccessful

From what i've read it would appear my hard drive has crashed and will need replacing. I purchased the machine on 16/11/12 and the warrantee ran out on 16/11/15. i have also read that i need to purchase a "Dell reinstallation disc with the same windows version that was factory installed". Unfortunately i don't have a clue about how to do any of that so i need some advice as to whether that's what's required; in which case i'll have to get a local computer guy out to help, or if not and there's something else i could/should try first, then your help would be greatly appreciated.

i apologise if i haven't provided enough info, so please feel free to ask if it would help clarify and i'll do my best.

Thank you