It isn't going to be easy, but just because something has not been implemented before, it doesn't mean its not worth pursuing, otherwise politics would not exist as a practice.
What people predict is purely speculative, but there is good reason to refute the simple explanation that a Corbyn government would amount to 'boom and bust'. What Corbyn proposes is a version of social democracy similar to the 1960s when many industries were under public ownership, education was free and rigorous. Before we suggest that this was 'the past', I would like to suggest that a more equal society acts against the bulwark of the inevitably more isolated world the UK will inevitably face if/when it exits the EU. This is not merely about redistributing money from rich to poor - its also a fundamental rethink of the way we think about what constitutes an 'acceptable' distribution of income and wealth. With unfettered capitalism, we have billionaires/CEOs earning unjustifiably more than the lowest paid of their companies - and Labour's policy is about minimising these unsustainable/immoral ratios by targeting the richest.
Labour's manifesto, however incorrectly one might interpret it, has actually fully costed its policies - unlike the Conservative manifesto which shirks from offering detail of its policies let alone how they will be costed, and completely shuns the impact of Brexit.