First you need to unlock your phone. Use this thread:
http://forum.ppcgeeks.com/showthread.php?t=42503
Next install your new ROM. It's really as easy as that. I am a Newbie as well but have burned about 10 or so ROM experimenting. The ROM has to be for CDMA and ideally you should go with one specifically for Sprint. I believe that Juicy's ROM would be a good place to start.
http://forum.ppcgeeks.com/showthread.php?t=58002
I've been trying pretty much only WinMo 6.5 and it's been very reliable. The easiest is to download a functioning ROM rather than a Kitchen. The Kitchen allows you to build your own ROM but I didn't really find it necessary. When you download the ROM you will first need to connect with ActiveSync or Windows Mobile Device Center and then run the ROM file. I can't recall the exact file name but I believe it is the only exe file. It will ask some questions to be sure you go through the correct steps and then it does everything for you and reboots the phone and then you are good to go with the new ROM.
There are lots of tutorials out there so if you are unsure then just poke around a bit. I was very nervous when I was ready to burn the first ROM but it was really as easy as can be. Granted, I did not have problems and some people do so perhaps I was lucky but was very glad I learned how to do it.
Good Luck