stiff alko hitch!!!

Hi everyone, i have a alko hitch 3004 fitted to my van and it is very stiff to push down and to relese, i went to the spring caravan and motorhome show today and spoke to a alko member of staff on there stand and told them my problem and the guy seemed confident that if i removed the three sets of two hex bolts on the hitch which removes the cover and wd40 the washers which should flex bit may not due to being left exposed to the weather for a long time which my van was for 18 months before i brought it, has anyone tackled this and is it easy as im sure i could take apart but worried about putting back together !! many thanks.