Is it safe? Will I 'brick' my phone? Yes, it's safe, and no, you won't brick your phone (most likely).
However! Palm strongly advises not to remove the battery whenever possible. You can initiate a reset by doing a hardware combination on the phone to do it:
1. Press and hold the power button (device must be on)
2. Switch the ringer switch back and forth
3. Repeat step 2
4. Repeat step 2
Wait a few seconds and the device should reset.
It is strongly recommended to not remove the battery from the device. This can back log the data for four hours, and in some cases removed stored information on the phone due to it being stored with data.
If you are having problems with the data on the device follow these steps.
1. Press the green phone key.
2. Tap on the Menu.
3. Tap on Preferences.
4. Scroll down and tap on Update Network Settings
5. The device will connect to Sprint Provisioning and update the Data Profile.
The battery doesn't seem to last very long (frequent internet/ texting/ etc use), so I was considering getting a back-up battery. Based on your comment below, will that end up causing me more problems?
Just make sure you turn off your phone completely before switching batteries, and you should be fine. Also, Seidio is already working on an extended-capacity battery (1350mAh, as opposed to the stock battery's 1150mAh), so you may want to look into that.