I believe there is a pressure relief built into the fluid circuit, but it has a tendency to either clog, fail or not evacuate quick enough. So Yes drilling in a bleed valve is a good idea.
Stiffer accumulator springs lower clutch slip during shifts, and because the pistons move less accumulator bore wear.
The larger boost valve and the separator plate are the big ones though, they triple the pressure to the third clutch, from 60 to 180. When the 80e's wear out over time that's usually the clutch to go.
There isn't much that you can do to beef up the reverse band, that's the other thing that fails in them. Mainly because its a band and not a flat clutch.
Gearcommand is just plain fun, puts a plug at the end of the manual valve and lets you hold any gear to fuel cut off, but will still downshift.
For what it's worth the 80e is an amazingly strong transmission, but it has some bad, lazy, soggy shifts. Tuning can help with this, but cranking up the pressure can cause that pesky high pressure parts breakage.
The install wasn't that hard, my trans had 117,000mi on it when I installed mine last summer. I'm 100% sure it didn't shift anywhere near as good when it was brand new. Has around 122,000 now.
Once you drive your truck with a SK you won't know how you managed to drive without it.
Here's my install article it never got stickied sadly.
When it comes down to it, is it really nessessary? No it isn't, but its good insurance.