Smooth transfer of name in Co-op Hsg Soc & Property Ownership

It's indeed enlightening to know if one has the right guidance, things do go smoothly. However, in my case, I would like to know the way to go thro' too: Lost my father at 10 mths. Lost my Mom on 12.12.18 w/o a Will. We are 4 Sisters & 1 Brother(Myself). However, in the House Deed the names of my Mother, my 4th Sister & Myself are there as she was unmarried when made. On submission of the DC, my mother's name was deleted in the Share Cert. But, my sister's maiden surname appears here. However, in the Property Tax Bill it shows, after My Mother's name as, vigare (meaning 'etc' in gujarati) while our Two names don't show, unless it is in the System database which is not shown by un-cooperative Corpn Staff. Pls note, 1st Sis married, but due to high diabetes has lost her vision & has severe trembling hands to sign; 2nd married, Expired; 3rd married & settled o/s state; 4th married & whose name is in the SC. Pls. guide: 1. How to go about it, step-by-step i.e. whom to approach first, a Lawyer, the Society or the Corporation? 2. How to change my sis's maiden surname to her post-marriage surname in the Society : a Notarised Affidavit with the DC or thro' the long Gazzette way? 3. If I intend to keep our two names, my Sis & Myself, as in the newly endorsed Share Cert even in the Property Tax Bill, do I still have to prepare a PedhiNama (Legal Hierarchy) & submit a Declaration from all the other fly members (sis's) to forgo their right or approve our Two names, Thanks in anticipation of a +ve response.