Sending a 110 lb amp to the manufacturer for cleaning/calibration. Good idea? How to ship?

The amp will most likely need new electrolytic caps throughout based on age. Once replaced the amp will indeed sound better. These do dry out over 20 years are don’t hold to spec any longer.  
This will cost, but it will help you keep the amp for many more years. It is always risky to ship so driving it there would be better. 
I would not bother with cleaning or biasing unless you first replace the old electrolytics. The manufacturer is most likely on top of this as part of the plan. 

I shipped an amp that weighs even more than that to the East (Classe DR3 VHC) but had an original double box. It came back in good shape via UPS, although I was worrying the whole time it was away that some idjit would drop it off a loading dock.

If you don't have an original box for it, suggest that you contact Simaudio and see if you can buy one.

Get a custom flight case made for about $400.00.

If you're servicing the amp, change the electrolytics. If you're not servicing, why open and change caps? Makes no sense for a 5 channel amp! Save your money and buy some separates. Amplifier, preamp along with a surround sound processor if that's what you want. Again, Simaudio is pretty good, I'll bet most caps still test in spec. This unit has 216,000 mfd capacitance in power supply. I've been fixing stuff for 50 years!

Hoping you take MC's advice....I cringed and smiled as I went through his sequence of events.  He is spot on!

I share this as a just how frustrating box shipping can be.  I know your package would not be as susceptible as my my company's but just an example.

One of my customers had a demo piece of equipment I sell.  It is essentially a 50lb egg about 16in diameter.  They saw the driver struggle to get it loaded on its Priority Overnight trip back to my house.  5 days later my regular Express driver casually strolled up my front steps(I saw him while on the phone and wondered...how???).

After my call I went outside and almost threw the box against the ceiling in picking it up.  It was empty!!  The $6000 piece of equipment, its power cord and the bottom section of packing were gone and a new diagonal piece of tape across the bottom flaps.  

At some point from pickup driver to delivery driver the damn thing fell out and the jerks just taped up the box and scanned it.

I am in the middle of the claims process now.  I have been very fortunate when shipping audio components out of necessity but man oh man it always makes me nervous!