Swaping HD to a different laptop question

My old (used) latitude d630 is toast due to the <ADMIN NOTE: Profanity removed as per TOU> nvidia video chip.  I need to get another laptop and save as much $ as I can.  I'm seeing more d620 laptops available in the used market with Intel graphics than d630's.  I don't want anything more with nvidia.  I think I've seen that the hard drive and caddy will fit right into a d620.  I can save more money if I buy used without a HD and OS.  My question is -  what is involved in putting my old HD w/ Vista Bus ed. into a d620.  What kind of issues am I facing.  Thanks.