Fan on central heating boiler (Glo-worm Ultimate 80) broken?

The fan on my central heating boiler (Glo-worm Ultimate 80) is broken and the engineer is telling me how difficult it is to replace. He says it will take him half a day to replace (ie. four hours labour). Is this really true? When he removed the cover it looked to me like a straight forward until removal and replacement. Is there something more complicated in the job that justifies such a long time?
Thanks for your interest (if there is any...)