The Gulf of Mexico oil spill reached the 100-day mark Wednesday as BP, the oil giant behind the disaster, made drastic moves, including replacing its gaffe-prone chief executive and selling assets, to repair its damaged image and rejuvenate its business.

However, a crush of challenges remain as the battered BP struggles to cover the costs related to the environmental catastrophe, repair its reputation, streamline its structure and deal with the various probes and legal actions.

The London-based company is replacing CEO Tony Hayward with Managing Director Robert Dudley, selling 30 billion in assets and setting aside 32.2 billion U.S. dollars to cover the long-term cost of the spill which has spewed more than 5 million barrels of oil into the sea and sapped about 40 percent, or 60 billion dollars of BP's market value.

Hayward was heavily criticized after he described the spill's impact as "modest," grumbled about wanting to have his life back, and attended a yacht race off the coast of England while American residents were busy grappling with gooey blobs along the Gulf shores.

BP said its whip will be handed over on Oct. 1 to Dudley, the first American to lead the company. Placing safety among his highest priorities, Dudley has vowed to learn from the oil spill disaster and to "change the culture" of how the company handles safety-related issues.

In addition to the CEO change, BP on Tuesday also reported a 17- billion-U.S.-dollar loss in the second quarter this year, after setting aside 32 billion dollars to cover spill-related costs.

Meanwhile, the company announced that it plans to sell 30 billion dollars in assets over the next 18 months to help cover its liabilities and streamline the company into a smaller, higher- quality business.

The sell-off would help reduce its net debt to somewhere between 10 billion dollars and 15 billion dollars within one and a half years, from the 23 billion dollars at the end of June, the company said.

But many analysts doubt the amount set aside by BP will be enough to cover the actual cost for cleaning the waters and shores, repairing local ecosystems and compensating affected residents and businesses.