This can be quite a big undertaking & unless you are quite confident in your plumbing, carpentry & tiling skills it is best left to a more experienced person to help or do it for you.
Of course carrying out the install is the last step on getting the bath/shower room that you desire on the budget you can afford.
Here are some steps you should consider as the first step.

* Think about the style you like
* Go through broachers for ideas
* Remember you can mix & match
* Keep in mind the size of your room
* Price check items from different suppliers
* Think on colour & tiles style/square meters required
* get sizes, to ensure the units you want fit
* Make a list & leave nothing off to get a true cost

You should always keep in mind that the new bathroom is an investment in your property, also that it is you that will be using it for as long as your at that property therefore it is worth all the planning & price checking to get what you hoped for.
Before you purchase any material you should get at least three estimates for the labour costs & at the same time you can find out if there are any problems with your new planned layout.
A new stylish bathroom should not cost the earth but a little bit of forward planning on your side will make all the difference on what it does cost.

Bathroom remodel is quite a big job so there will be disruption but then again you can not make a cake without breaking some eggs.