Hi Pete2013,
You will undoubtably be walking through a lot more than just mud on the way to Hollin Hall

but sometimes the cows (especially if they've just put a new herd of youngsters in) find walkers absolutely fascinating & you end up being stampeded up & down the hill! Having said that I always take my dog who is a bit of a cow magnet, so on your own or with human company it might not be such a problem.
I'm pretty sure the original farmhouse wasn't demolished, if you look very carefully as you walk past on the public footpath you can just about make out the original house within the present building, I always feel it's like it's been engulfed by extensions & mock stately home features but if you look really hard it's still there peeping out.
As for the barns, the stables where Steve slept have been turned into a cottage (interestingly this was originally a house before YTV moved in, if you have Janes book there's a photo of the site as it was) the small stables adjoining this have gone & the big old barn where Jane told us the cast & crew ate was demolished because it was 'unsafe'

(there is a very old map on display in Harewood House, I think from the 15 or 1600's with Hollin Hall on showing this old barn!) There is now just a large wall, the owner said he was going to have a wildflower garden there. The top two barns which had the blue doors where the hayloft was have had a lot of building work done but as we can't get anywhere near them now I'm not sure what has been done to them internally.