I am making a choc mud cake and covering it with chocolate ganache and dressing the sides with pistachio praline.

My question is... how far in advance can I put the ganache and praline on without the praline going sticky? And should I store it in the fridge? And will the ganache lose it's gloss or go whitish if in the fridge.

Thanks for your advise - it's a special cake and I don't want to muck it up!!