Automatic Transmission: You'll need to check the fluid level indirectly, often requiring a mechanic's expertise and specialized tools. The fluid level is usually checked at the transmission cooler lines or via a specific access port (if it has one) when the transmission is at operating temperature. This is not a DIY task for most people. Incorrectly checking or filling can damage the transmission.
Manual Transmission: Manual transmissions generally don't require regular fluid checks unless you suspect a problem (leaks, unusual noises). The fluid is typically changed at significant mileage intervals (consult your owner's manual). There's often a fill plug (and drain plug) on the transmission case, but these aren't used for regular "checking" in the same way as a dipstick.
In short: For either transmission type, the best way to check the transmission fluid is to take your 1996 Pontiac Sunfire to a qualified mechanic. They have the tools and knowledge to properly assess the fluid level and condition. Trying to do it yourself, particularly with an automatic, risks damaging your transmission.
