Steam is awesome and also a BIG friend to the Linux community. You also get to use your Steam games on any machine you own. It keeps everything synced for you. Half-Life on Steam is cracking good. Its an oldie but a goodie. I highly recommend it. It runs great on older and lower spec machines. You won't need an all singing and dancing video card. I've only got an,
Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) and Half-Life rock with it. It cost me €10 so it will be about the same in dollars. It really is well worth it - totally addictive

Here's a good command to find out what video card you have:
lspci -k | grep -A 2 -i "VGA"
This is always good to know when you are looking at purchasing games - have fun

!!