Hi Danielle
Since John & Margaret's deaths would be before 1855 there would be no formal records of their deaths. Statutory registration of Births, Deaths and Marriages did not begin in Scotland until 1855.
Prior to that date the only records were of births, or more usually christenings, and marriages - again the posting of Banns rather than the actual marriage itself.
Some parishes kept a record of deaths and/or burials. Others kept a record of the hire of mortcloths but these records are patchy across the country.
The most common way to find information about deaths before 1855 is to check Monumental inscriptions once you have established where they lived and which graveyard they might be buried in.
Some Local & Family History Socities have already done some of the work by compiling lists of Deaths, Births, Marriages but you would need to join the society (Most are around £10/year so its not too expensive) or they may sell books or CDs of the records to non-members.
Russell
