There are various ways to do that:
boot a myHack USB installer that had the lspcidrv kext in /E/E -> should allow you to open up a Terminal window to type lspci -nn command
If the PC still runs Windows, look at the various devices listed in Windows Device Manager
use various Windows tools such as those listed by Dinesh in his R&D->DSDT/SSDT thread
look up the published specs in the user manual (available off Dell's web site)
etc, etc.
Generally speaking, the main things to look at include CPU model, chipset (HDD controller), amount of RAM, model of graphics card (whether built-in and/or PCIe add-on), HDD type, audio chip, LAN and/or wireless card model, BIOS version (the BIOS settings can be important too).
Have a look at the description I had made of my Precision 670 (a model much older than yours) in the EDP->Supported Models with Guides->Dell forum section.
By the way, didn't you ask the same questions about ML for that particular machine in that same section last summer?