A basin wrench is crucial because it's specifically designed to reach and loosen the mounting nuts that secure the faucet from underneath the sink. These nuts are often in very tight, awkward spaces where a regular adjustable wrench simply cannot fit or get enough leverage.

First, try applying a penetrating oil to the corroded nuts and let it sit for 15-30 minutes to help break down the rust. If they still won't turn, you may need to use a small hacksaw or a specialized nut splitter designed for plumbing to carefully cut through the nuts. Always wear eye protection when doing this.

While 3 hours is a good estimate for an experienced DIYer, beginners should budget a bit more time, perhaps 4-6 hours. This allows for unexpected challenges like stubborn old parts, cleaning time, and carefully familiarizing yourself with the new faucet's instructions without rushing.

The most common culprits for leaks are loose supply line connections or improperly tightened mounting nuts. Gently but firmly tighten these connections with your adjustable wrench. If the leak persists, you may need to disassemble the connection, inspect the washers/gaskets, and reassemble with plumber's tape or a fresh application of plumber's putty if applicable.