Change from 3 to 7 gears- how???

[Love beach cruisers]

Hi!
I have Kokkedal beach cruiser with 3 gears (Shimano Nexus). I am thinking about changing it to 7 gears. Do you know if it is a big deal to do it? Is it expensive???

Many thanks!

 

[tyred]

I don't know much about the Shimano hub gears but I would take an educated guess you require a new 7 speed shifter and to have the wheel rebuilt with a 7 speed hub and it is likely to be expensive.