That is a great deal, and sounds like you're dealt with a stand-up seller. Doesn't get much better than that.
Regarding the steering box, there are a lot of great reviews of steering boxes from a company called Redhead Steering.
https://redheadsteeringgears.com/
As for your Quigley, most everyone on this forum agrees that a significant improvement in handling can be achieved with the Ride Improvement Package (RIP) developed by Agile Off Road. You can install it yourself, have a local company do it, or plan a roadtrip to San Diego, CA and have the company install it. If you head to San Diego, they're almost right next door to Aluminess which make some gret aluminum front and rear bumpers.
https://agileoffroad.com/rip-quote/
FWIW however, I have not had any personal experience with either upgrade.
Herb