Stage 1 will take you to a very important headstone to me, I miss these two very much. There is no physical container here, you just need to collect some numbers.
Add Dorothy's birth month, day, and year together with the day/month/year that she passed away. Add the digits of the month/day/year of the day they got married. Take this number and add 626. This will give you abc.
Add Isaac's birth month, day, year together with the day/month/year that he passed away. Add the digits of the month/day/year of the day they got married. Take this number and add 134. This will give you def.
The coordinates for the cache can be found at N 40 54.ABC and W 096 31.DEF
Only use the last 2 digits on the years