Hi Lisa,
The only conclusion you can draw from being given a home assessment is that someone has decided that you have a level of impairment that warrants it.
The process will be the same as any assessment held in other venues. This is explained in the PIP guides.
It is up to you which room the assessment is held in and who you have with you. You do not have to make any special arrangements and you do not have to get out of bed if you would not usually do so.
The assessor has no more rights than any other visitor to your home. They cannot 'snoop' through the rest of your home without permission - and we have never heard of anyone asking to do so.
Nothing on this board constitutes legal advice - always consult a professional about specific problems