So far, the project team at Stanford has been fairly "No Can Do" about this.  Your previous work won't disappear, but so far, they haven't allowed a name change with carrying over the same data.
 
However, reaching out to the team directly on Twitter or Facebook (if you wan't a message to go to the team, don't rely on the forum over at foldingforum.org - It's a hit or miss as to if the message gets delivered) may yield different results.
 
d

All you need to do is email the Webmaster@EVGA.com and they will take care of it for You.
This is Monday Morning and EVGA is not open on the Weekends.

Mac.Concierge
folding at home username, not EVGA Forum username.

OK and what is your Folding User Name?
Because this You Can Change under your My Profile bottom of your Settings.
My Profile
 
 
But this " Is there a way to change the username and retain the 308+ Million points I had?" Is not under EVGA Control.
And Folding @ Home will not correct it for any member.
The same goes for the Team you are Folding Under they will stay under you Folding Name but will not show under a New Team.

Mac.Concierge
How can I change my username (donor name)?
The simplest way to change your username is to go to the Configure window (click the Configure button on the upper left corner of the screen). You can change your username at any time. However, old work units will remain credited to the old username.

Correct
 
Your Question "Is there a way to change the username and retain the 308+ Million points I had?" is not under EVGA control and no one here can help with this.

Mac.Concierge
I get they don't want to do the name change because it would be so much work for them if everyone just request it.

But for me it's 14 years and 308 Million points of existing work too.

Who?
EVGA or Folding @ Home?
 
What Name are you Folding Under?

We TOTALLY understand that it's a reflection of a GREAT deal of time and effort. There isn't a single one of us old timers (I've been folding in some way shape or form since 2005 or so, personally) who haven't thought of making a change that effects that. Myself, I started with TeamPimprig and was VERY hesitant to fold for another team, but in 2010, I decided to just make the jump. It doesn't mean I didn't DO that work, I just fold HERE now.  So, you can either decide to cut the loss and start with a fresh name/team combination, OR, stay with what you have now and deal with not updating.
 
Again, if you are serious about approaching the Stanford Folding team about keeping your numbers with a new name, feel free to go to their Twitter or Facebook accounts and contact them direct.  This forum is merely for the EVGA Folding team, and is NOT directly connected to the Stanford Folding project, nor are anyone here able to help you switch your name but keep your points.
 
Thanks!
 
d

Been folding since 2004.  I folded as chaosdsm for many years for MaximumPC (team 11108) before coming over here.   For about 2 years, I was splitting my folding between the two teams, there under my orginal folding name, and here under my current folding name.  I've also folded more for other users that I did for my original name while at MaximumPC. 
 
Just after our unofficial leader passed away in early 2012, I folded 10 million points under his username with a brand build utilizing a 3930K processor & GTX-460 GPU.   Gordon was truly the glue that held MaxPC together, so much so that we (the greater folding community, not just MaximumPC) donated enough money to Stanford, that they were able to purchase two new server units & name them in memory of Gordon & his wife Rose.  Without him, the mood/vibe of the team had changed so much, that by the time the GTX 660 was released I decided to leave MaximumPC & fold only for EVGA. 
 
In the end, its the work that is completed that matters, not the username.

Yes, it is too much to ask.  They won't do it.  Plain and Simple.
Sucks, but that is the truth.