My rollover was a 401k but I believe the process is the same. The key thing is to make sure the money is going from the 403b trustee to Vanguard as the IRA trustee.
In my case, my 401k plan sent me a check made payable to "Vanguard FBO pb4uski" and I then took a photocopy of the check and sent it to Vanguard along with a completed form to have it deposited to my existing IRA. Vanguard reps will help you through the process.
In my case, cost was zero.
If you're looking for a 50/50 AA then equal parts of Wellington and Wellesley would give you a ~ 50/50 AA and would be easy. Wellington is ~60/40 and Wellesley is ~40/60. I'm ~ your age and am 60/40 but there is nothing wrong with 50/50.
If you have substantial taxable and tax-deferred monies, you may want to consider tax efficiency - carrying bonds in your tax deferred account and equities in your taxable accounts. Vanguard can elaborate or you can read more about it here