Did you complete the ICP? Do you have any evidence of completion of the course - such as any form of certificate? If so, then I would expect that you would not need to repeat the course.
You will need to do First Aid.
You should start as if you were a new registration. While your records from 5 years ago may exist somewhere, as are an inactive minder they would have been filed away somewhere. So best to start from scratch, and if the regulator is able to match your new application to old records, so be it.
So contact your local Children's Information Service and speak with them about registering as a childminder. They can then point you in the right direction for your particular area.
If you want to use registers / accident books produced by NCMA, you will need to become a member of NCMA and then you can order their member publications. However, you do not need to be a member of NCMA to be a childminder, so you could devise your own registers, accident books etc.
You will require Public Liability Insurance. This you can obtain through NCMA, or through Morton Michel who also provide Child Record Forms, Registers, Accident/Incident Record, Contract packs and other publications.
As part of a new childminder application you will need to do a Health Declaration (the form is in the Childminder Application Pack), which will involve contacting your Doctor (who may impose a fee for completing the paperwork, which can be up to £100 if I recall rightly). Contact your doctors surgery for their current list of fees.
With 3 children aged 8, 6 and 3, the maximum number of under 8's that you can mind will be 4. Depending on your specific circumstances (such as house size) you may given a lower number. Typically your registration will be for 6 children (including your own) under 8, of which 3 children may be under 5, of which 1 child may be under 1.
The above I should point out is for those in England. If you live in Wales, Scotland, Northern Ireland, then local procedures may be different.