“If there is a recession, how long will it last, and how bad will it be?”
The answer to this question is in the power of the government. As the economy goes into recession more people save due to worrying about the future and investment falls so there is less money in the economy to buy goods and services. The cycle repeats itself until the economy settles into some kind of unemployment equilibrium if there is never anything on the horizon to improve expectations and encourage investment. So to answer the question, given the shocks of the oil price rises, and food, this would be expected to be the start of a long and bad recession.
However, there is a solution. The government can intervene by employing the labour that the private sector does not want. This will also mean that a reasonable level of demand can be maintained in the economy so that the recession will be shorter and less bad. Also, the government can increase the size of the public sector by nationalising utilities and public transport. The smaller the private sector, the smaller the impact of the recession.