Wheelchair access + house extension

Hi all,

I've two queries here so just looking for general advice really.

1) If someone wanted to get wheelchair/mobility roller access added to the back door of house, do you just call a builder or are there specialists in this area?
Back door to house has lip at bottom of door frame and two steps so looking for the exit to be levelled off with a gradual declining railed ramp to allow my mother exit safely and out using one of those mobility rollers. Seems fairly standard for this sort of thing. I presume the common concrete one is the safest way to go. Just wondering who to call? Don't want to call any old builder who hasn't got the experience of disabilities in mind or is that exactly who to call as it's a straight forward job?

2) To add an extension to a house (country bungalow with lots of space around it so site is no issue) let's say a decent sized bathroom and a bedroom and small living area (so three extra rooms), what would a very rough estimate price be? And I appreciated this is a hard one to answer so I'm just looking for something like 40-60k or 50-80k or 80-100k or 100k+ ?
Area is West Waterford if that helps.

thanks all!