You almost have it.
The TEW-623PI is a TRENDnet PCI wireless adapter. The only problem is that there are two different versions, which require different drivers. Look again and see if you can see whether you have Version 2.0R (info and driver download HERE) or Version 3.0R (info and driver download HERE).
The installation for these files is quite a bit easier: there's a Quick Installation Guide (scroll down the page and click the link).
Actually, the Quick Installation Guide wants you to install the driver BEFORE the device is physically installed in the computer. So, turn the power off, touch the case with your hand to discharge any static electricity, and carefully remove the card. There probably will be one screw holding the card in (if the screw is present, it will be in the slot at the top of the bracket -- see arrow):
Then gently but firmly pull the card up. It probably will be easier to remove if you unscrew the 3 antennas. You may have to pull one end of the card up first; just don't rock the card side-to-side.
Once the card is out of the computer, you should be able to more easily see if you have version 2 or version 3. And, while the card is out and you have more room, do yourself and your computer a favor: buy a can of compressed air and blow out all the dust.
The download from Trendnet installs a configuration utility for the adapter. To learn how to use this, download the User Guide, link at the bottom of the support page.