I normally remove the fan by jacking up the truck and dropping it downward, but it can alwo be removed from the top. This video shows a top removal process. SSRs may or may not have bolts, all the trucks I have worked on have had zip ties used for the mounting. Not a big issue as the mount tabs are rather large and it would take a lot of force to get them to jump out. But, I have never heard of one fan falling out, not sure if it was an OEM or incorrectly installed aftermarket.
Here is a good video of a top removal process – https://www.youtube.com/watch?v=kTS_qmhL4Bo
Also – https://www.youtube.com/watch?v=VugEWlWRVDM