Omistep - Replacing. Which One?

Hey guys,
I have a manual Omnistep on the rear of my Pollensa, (1999 Peugeot A.S.Pollensa) and at some point in it's past the step has ben "Dunted".
I want to replace it with a 12v motorised step but have a bunch of questions.
What point do I measure the step from to get a replacement? I've seen some on Ebay at 550mm / 500mm and 470mm - but it doesnt state if that's the size of the step or the fixing plate, you know from bolt hole to bolt hole, cos on my step, the step is 470mm but from hole to hole is 520mm. It's all very confusing to be honest.
Does anyone know of any non-omnistep steps that may be cheaper? or should I stick with Omnistep?
Do the steps come with internal switches? I ask that because again, the ebay ones are a little vague and there are switches on sale so me confuddled.
Are they easy enough to fix? I'm thinking it's a case of hooking it up to the fuse box somehow..... I may leave fixing it to someone who actually knows what they are doing lol, but any advice would be welcomed.
Many thanks.
BB

Hi Buster

Guessing not too many of our members are familar with this kind of setup as I'm sure you would have had a reply by now
Think the best bet is get someone to supply and fit leaving them with the headache of getting it right!
Hope you get something sorted soon anyway

CC

I've elected to do the smart thing, as CC suggested, give someone else the headache and get a 12 month warranty in the bargain.

Knowing my luck I'd wire it up so when the step is supposed to come down the loo would flush!

Thanks for the replies guys.

BB