Is there such a thing as a site/sight gauge located somewhere on the 850
so that one can view any bubbles in the system, which usually means you need a refill?

134-A will show "bubbles" or "foaming" in a properly charged system. This is why a sight glass is NOT used in these systems.

No such thing on the 850. Many have said that the only way to correctly fill the system with refrigerant is to evacuate and refill with a machine that can accurately weigh the fill. Many others seem to have good luck just refilling using the kit and gauge. I think that I wouldn't want to try it without the pressure gauge. If you over fill the system, then you will have more problems. BTW, the pressure will cycle as the compressor cycles on and off. The correct method with the gauge (per earlier posts) is to use the low end pressure reading. It is easier to understand if you have the gauge attached, i.e. it should be in the blue at the low end pressure reading, not the high end.

Those sight glasses are comon on old R-12 (freon) systems but rarely if ever used on a/c systems using R-134A as the refrigerant. Nearly all 850's have a/c systems with R-134A so you won't find the sight glass.

Jim