I made this jump 2 years ago. Big difference between Duron850 and Athlon T-Bird. Here is a 1.33>>> http://www.newegg.com/app/viewProductDesc.asp?description=19-103-156&depa=1
While you should hone up on your knowledge of hardware. I wouldn't recommend a rookie to perform this task.
I want to max out my Gigabyte 7IXE4 motherboard. I currently have a Duron 850Mhz and want to go up to a 1.4Ghz. Yes I know it still isn't that fast, but getting a new motherboard is not an option. I wanted an Athlon Thunderbird 1.4Ghz, but I'm not sure if I'll even be able to find one anywhere. There's the Duron 1.4Ghz, but that would require a BIOS upgrade, which I've never done before and could be risky. My mom also uses this computer for important things so if I were to mess it up it would be hell. There's also the option of an AthlonXP, but I'm not sure if the motherboard will support it. The FAQ on the Gigabyte website says that the board supports Duron and AthlonXPs, but on the same website there is a processor compatibility chart that doesn't list any of the XPs as compatible. I'm not really sure what to do and could use some advice as to the best path.
Thanks
Adam

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic