@ecterrab
Hi there thanks for getting back. Ignore that line with Riemann[alpha,beta,mu,nu] etc., i was just experimenting and forgot to delte it out, oops.
I am effectively trying to reproduce the second equation shown in the below image by starting from the general expression from the Riemann tensor, lowering an index with the metric tensor and then use Riemann normal coordinates to work at a point on the manifold where I can treat it as being locally flat. This should make the connection terms zero but not their derivatives. All this should lead to the simpler second expression below in terms of the metric and its second derivatives.
The tetrads package you mention looks like it might offer just what I need, I'll have a read.
Thanks again!