Indian Passport renewal and name change

[oye_rg]

Hi,
My spouse's passport expires in Feb and she will be applying for renewal soon. I have a peculiar situation though and am wondering if someone here can advise.
Her current passport carries only her name and no surname (the surname is blank). Her ILR stamp also carries only the firstname and no surname. I do have the original marriage certificate which has a surname under 'name after marriage'. My queries are as follows:

1. Does adding a surname when none existed considered as name change needing newspaper advertisement etc? Or would the marriage certificate be enough?

2. Can the name change be combined with passport renewal? Do I need fees for just passport renewal or also for name change?

3. If she only applies for a name change would the validity of new passport be same as existing passport or reset to 10 years?

I know this situation is rare so there may not be a definite answer but any best guesses or advise would be useful. Is it worth getting the surname added?

Thanks in advance
P.S. We will be applying for British passport 6 months later if the name change could pose any problem there.

[oye_rg]

UPDATE: She kept her name without the surname until naturalisation. At NCS, we changed the name showing the marriage certificate as evidence. Changing name at time of gaining british citizenship appeared to be easiest and smoth as compared to other options.