If you can carve out the time, make sure you head over to Lionel Windsor's blog and spend some time on working out 'covenant':
The larger import of this for Paul’s argument with his opponents is that the covenantal obligations laid upon Abraham (circumcision) and his national seed (the law) as a prerequisite for international blessing are not laid upon the nations as a prerequisite for their own blessing. Abraham’s seed has fulfilled the covenantal obligations. The multitude of nations, therefore, are not called to enter this covenant, but to find blessing in the “seed”, to be “immersed” into Christ, to be “clothed” with Christ (Gal 3:27). This comes about by the Spirit and by faith in Christ (Gal 3:14).
I've skim-read, but will be coming back, God willing, to re-read.
The other thing to say about Lionel is that he doesn't always write technically. In fact, here he offers translations for the rest of us.