To remove the rear turbo, I found it easier to remove the front and dump pipes. But it was more of an exploratory venture than a quick remove-to-replace-gasket job.
I bought short/stumpy ring/C spanners, helps with taking the dump pipe off.
Rest is fiddly and slow, but doable within a day.
Remember to take the water lines out first.
What mods? Standard ECU? What's done to your S13?
Lots of things can be a factor.
You'll probably want to change the turbo to an OP6 or bigger, and get injectors + fuel pump + tune.
Was going to ask, how the Canadian dynos compared to 'Murican ones.
I'd focus on getting rid of those shitty sponge pods (either standard air box with paper filters or APEXi/similar paper filters) and getting at least N1 turbos + tune.