For an overgrown Concord grape vine, the best approach is a drastic, dormant pruning in late winter or early spring. Cut the entire vine back to a short trunk, leaving just a few inches above the ground, and then prune the new shoots that grow in spring to one or two main canes for retraining the vine. For a less aggressive approach, you can prune to a single trunk with a few one- to two-year-old branches, trimmed to a manageable length and trained along a trellis.
Here are some tips for caring for grapes in Oregon: Choose a sunny spot that's sheltered from frost, like a south or southwest slope. Avoid heavy clay soils or soils with poor drainage. Plant bare-root or potted plants at the same depth they were in the nursery. Firm the soil around the roots and water thoroughly. Keep the soil moist but not saturated. Water weekly. Prune dormant grapevines in winter, ideally from December through February. Pruning reduces the number of vine buds and aligns growing points with the intended training system. Keep the planting free of weeds. Cultivate shallowly to avoid damaging roots. Use mulch to reduce weeds and increase soil temperature.

Check out this publication:

https://extension.oregonstate.edu/sites/extd8/files/catalog/auto/EC1639.pdf