Not very... depends on how you do it mostly :wink:
When I ran conventional springs in my car I always would take out the rear 12mm bolts out of the subframe and slowly lower the back of the IRS (this of course with the car on jackstands and a floor jack underneath the subframe) and the springs would just fall right out. You might need an extra set of hands getting them back in when jacking the subframe back up, but it isn't that bad. Of course doing it this way I always dropped the catback down... but then again that's not really difficult either.
There are a few other ways to do this as well... I'm sure someone else will give an example. Whatever you do don't drop the entire subframe just to do the springs!! You'll have one hell of a time getting it back in if you do :dumb:
it was pretty easy in my case. I removed the shocks on the IRS where they bolted up. Then I unbolted the exhaust hangers at the tips. After that I placed a jack under the IRS and removed the back two IRS frame bolts and then tilted it down. The springs fell out.
i used to just use the spring compressors, remove wheel and shock bolt on lower arm and let lower arm as far down as it goes, zip up the spring compressor w/impact and pull springs out. some lowering springs dont require spring compressor to install or to remove, my kenny browns dont. and thats with mm isolators. with stockers i needed compressor to remove, tried pry bar but no way