Drop the quill down a couple of inches. At the back about an inch up is a small grub screw, remove this, then check it's the only one in the hole. Bridgeports have a nasty habit of fitting two screws in the same hole to lock them but I'm sure this one is that shallow it can only hold one. Then unscrew the ring at the bottom, genuine Bridgeports use LH thread, some clones RH the better Taiwanese close LH again.
Once the ring is removed the spindle will cone out of the quill by tapping down. Sometimes if the bottom ring hasn't been fully tightened wear can take place giving more plat and often just tightening up will suffice to remove this.
There are a pair of matched Class 7 ABEC angular contact bearing at the bottom and a standard deep groove ball race at the top.
The angular contact bearings have spacers in between the inner and outer to set preload, the should show no signs of spinning or wear on the faces.
Don't know where you are but if you get stuck for service or repairs try these people.
**LINK**
Good lads, do a cracking job, know what they are doing and carry a good range of spares.