1. Depending on your rom/radio, you still may need to use a primer. I would recommend GPSViewer. I believe that when you use GPS, it will remember the last location you were at. So if you use it from home to go point A, and you turn it on again from home, googlemaps is trying to locate your device around point A (which can contribute to the more then 2 minute locks). Using a primer will help. Check this post
http://forum.ppcgeeks.com/showthread.php?t=24979
2. The only real noticeable upgrade to the system is the threaded sms. There are a bunch of behind-the-scenes changes, such as the GPS being enabled and upgraded radios, but other then that, not much else to my knowledge.
3. The icon on your screen is most likely suppose to lauch Telenav. Which is the Sprint GPS program, it's great and you can try it out for free for 2-3 days. If you have an unlimited data plan, it may be include, if not I believe it is $9.99 per month. It will work on the official rom upgrade, if you are on a custom rom, the chef may have not included the app which is why the button does not work.
4. Almost all the new roms will save camera pics to SD by default. You just need to make sure you hard reset after installing, and that the SD card is in the phone.
Good luck!