I never remove the carb to change the squirter. Just use a screwdriver and a pair of needle nose pliers.
As to changing the spring: you'll need to remove the carb. Too much going on not to. You'll want to do it on a bench. That's why they make the quick change kit.
The secondary spring is in that part that hangs off the carb by the choke. You have to remove the choke to get to the last screw to remove the secondary actuator.
Have you pulled your plugs yet after driving it normally? Drive it around (don't flog it because you'll get into your secondaries) and shut it down as soon as you pull into your garage. Let it cool a bit (or don't let it cool like me...) and pull a plug to get a reading. That'll tell you if you're too rich or lean. Also tells you about your timing.
Thinking it out a bit it could also be your vacuum advance. Either one will result in poor power.
