Make sure it has the 33.004 software and all the accessories for self-tests and various ways of powering it up and hooking it up. Your choice on getting the case or not.
I have used mine almost daily since 2017. In that time I have replaced the OBDII adapter a time or two, the cable, the VCI Module and even the PCMCIA card with the software on it. The Real Time Clock quit passing the self-tests years ago and changing the internal battery didn't make a difference. In reading the comments, a lot of dealerships and shops bought the same replacements parts for their "genuine" articles as I did from Amazon. Stuff wears out.
You will also want an adapter to connect the Tech-2 to a modern computer if you want to program modules. Below is the one I purchased and it is plug and play. Since then, another member located another that is plug and play also for much less but I can never remember who or what!
You do not NEED the TIS2000 software and "key". This software will work for updating GMT800 and other vintage vehicles and you can download a "snapshot" from the Tech-2 to view it on a computer screen which is nice. It is a pain to install and requires an older machine running XP or Windows 7. I have videos on my youtube channel showing this.