Bricks, Masonry, Asphalt and Concrete - Repairing minor water damage to concrete block chimney

We are purchasing a home with a concrete block chimney that serves a wood fireplace. The inspector noted cracks from water damage, which he says are minor but suggests repairing, as they could get worse quickly over time. A mason wants $2500 to do the work (including tearing off and replacing the top few layers of blocks.) That cost is a bit much for us right now, since the house already needs another $10k or so of repairs. Plus, we are considering converting the fireplace to gas sometime in the next few years, which from my understanding can vent right out the wall and doesn't need a chimney, so it's possible we may just tear it down at that point.

So, my question: Is there something we can do ourselves now to slow the spread of the water damage for a few years, at which point we would either get it professionally repaired or torn down? Can we just patch the cracks, add a new mortar cap at the top, then install a wide steel chimney cap to deflect the water? We don't have experience with home repairs, but we have family members in carpentry and construction, and we're willing to learn and get dirty!

Thank you!