To answer your questions, here's what I know & some of what I have been told....

The new wings do not have the fwd or aft carbon pins installed. You decide the incidence you want. The complete new Ultra kit wings have +1 to +1.5 deg to help take-off & landing. My classic took a while to rotate on take-off, so I'd copy the Ultra's incidence.

New fuse has bigger inlets for bigger turbines. Although guys have run P180/200's in the classic fuse with no issues. The new vertical fin is rounded to match the new wings. Total length with new stab is 107" - classic is 102"

The new wings are swept farther back thus shifting the cg & eliminating all or most of the nose weight needed with the classic. Plus the new wingspan is 90" - classic is 81.1".

The wings also have wider gear doors for the new trailing struts. The new trailing struts are offset aft. The wider doors actually give you more options for gear. Only straight trailing struts fit the classic wings.

If I were in your situation, I'd definitely get the upgrade kit. Pretty cheap for a new set of wings & stab on a jet this size.

I actually just sold my Lightning - had I known the new wings/stab were going on sale I'd have probably kept it.
It's a great airplane & I'll most likely get another one........