We did it in our old house, on the advice of my Dad who said that as long as you're not planning to move any plumbing fittings (ie. change the position of the bath/sink/etc) it is just a case of replacing like with like. He was pretty much right tbh altho it was bit of pita maneuvering the old stuff out and new stuff in (but our bathroom was v tiny). We used flexible connector pipes which can be bought from DIY stores and so even tho the taps on the new suite weren't in exactly the same place as the old ones they connected up easily. hth
We kept most of the old tiling as they were plain white but had to redo around the bath and sink where tiles got damaged when we got the old suite out. We did most of the bathroom using this book which since moving again have found invaluable!
DH did ours (with a bit of help from me) and mostly it worked well. It took him a little while to figure out how to do the top part of the toilet, so we had to flush it with buckets for a couple of days, but then he got that sorted and put in the sink and bath without any major problems, except one that wasn't really his fault:
After he had swapped the bath and sink, we had a big leak that went through the floor to the kitchen. But it wasn't from any of the bits he had touched - it was from a joint on some of the old piping, further along from where he had done the work. It seemed that the movement and vibration from cutting the pipes further along had somehow weakened the old joint and then it suddenly failed. So just watch out for any possible weak points even in the bits you are not changing!
The only bit I wished we had not done ourselves in the end was the tiling and sealing round the bath; it was the first time we'd done any and it just looks a bit amateur compared to the rest of the bathroom. The bit around the window was especially hard and we ended up cutting across some tiles as we didn't know how to take sections out of them neatly, which doesn't look as good as a professional job would have.
my dh is more than capable. however we have held off doing it till we have more money. he says, we have to budget for contingencies. ie if we pull the tiles off the wall and the wall then needs making good, there is potential plastering costs. You also need to factor in the cost of the associated bits such as pipework, fittings, caulk, grout etc etc into the cost of the suite and tiles.
We have dodgy plastic tongue and groove on our ceiling too, which is fitted around a cupboard so if we took the cupboard outm we would need to remove the ceiling and god only knows what we would find underneath !!
He IS a pessimist, but I do appreciate where he is coming from
as we've decided to sell, we've spent the weekend prettying it up - regrouting painting and laying vinyl flooring - it looks like a new room. However, he's spent most evenings and all weekend doing it - and he knows what he is doing - so be prepared to factor in extra time as well. ie your bathroom will be unusable whilst grout dries etc etc ! hth