If you own a Saab you will likely have to replace its battery at some point, perhaps several times; this is the case with any car. The shelf life of a Saab battery may be lowered due to damage or to everyday mistakes such as leaving the car headlights on by accident; on the other hand the battery may simply have reached the end of its lifespan.
There are some signs that a battery may be dying and needs inspection, such as the car's headlights becoming dimmer than usual. Individual batteries are also designed for certain climates, and if you move to an area with drastically different weather conditions then it might be a good idea to look into finding a new battery.
If you need to change your Saab battery then you can find help at a service shop. Alternatively you can do it yourself for free; first, turn of the engine; then prop the hood open, and cover the Saab's fender with a blanket or something similar to protect it from any battery acid that may leak. After this carefully detach the negative terminal, followed by the positive. Next, remove the hold-down that keeps the battery in place, and finally remove the battery itself. Installing the new Saab battery is a fairly straightforward process of inserting it into the same location as the previous one and re-attaching - in order - the hold-on, the negative terminal and the positive terminal.
If you do this carefully and follow professional advice your Saab will have a new battery and will be ready to roll one again.