Self Assessment for a deceased relative

I am applying for a Letter of Administration for a deceased cousin and I am the nearest living relative. Without the Letters, I have obviously received very little information from financial institutions but I have received a "Chargeable Event Certificate" and after consultation with HRMC, they have sent me a 6 page "SA100 Deceased" Tax Return form to complete PLUS 6 pages of literature not in a format normally used for completion but referring to a form with boxes to be filled. My question is; Do I only need to complete the "Chargeable Event" section of the form and sent it to HMRC or have HMRC not sent all the necessary paperwork that needs to be completed.

Hi Andrew,
The tax return will need to include all world-wide income and capital gains tax from 6 April up to the date of death of your deceased cousin.  
Income and capital gains after the date of death, is part of the deceased estate.
Thank you.

Thank you for the response. I have since found out that I wasn't sent all the necessary forms to complete, which lead to my query.