I bought

Thief:Deadly Shadows
Thief II:Metal Age
Thief:Gold

And have downloaded everything they have listed with the GOG Downloader.

What/Which mod do I need to install, if any? (TFix? Something else?)

In what order should I play the games?

If it matters, I'm running Win7, 64 bit.

Thanks in advance for any help/advice/tips!

chronologically, most definitely - the first three games are one story that starts with T1 and ends with T3.

use;

TFix
TafferPatcher
Sneaky Update + Thief3 Gold

All right I have run TFix, and just downloaded TafferPatcher, but where do I find the last one you have listed?

you google it.

http://www.ttlg.com/forums/showthread.php?t=138607
http://www.ttlg.com/forums/showthread.php?t=143659

OK, followed the links and installed them, thank you!

EDIT: Nevermind, once I checked the original download Zip files, I can see that Thief:Deadly Shadows = T3 and Gold is indeed T1. Got it now.

Listen to voodoo, he knows what he's talking about.

Also, I like to recommend playing at night or at least in a dimly-lit location.

Don't even worry about The Metal Age and Deadly Shadows yet. Finish the first one first.