The LGB 00559 provides some tips for rack operation:
Rack Railway Tips
• To avoid abrupt transitions, use several short straight track sections, like 10150 sections, at the beginning and the end of a steep section. Slightly bend each joint vertically to create a smooth transition.
• For overhead catenary operation on steep sections, use the 56300 tilting catenary mast. The masts should be spaced closer than on level track.
• To avoid accidental uncoupling, 64462 coupler hooks are recom- mended for rolling stock used on rack sections. Also, "symmetrical" coupler hooks should be installed on both ends of all rolling stock.
• LGB rack locos can be used on rack sections and regular "adhesion" sections.
[COLOR=rgb(99.800000%, 8.600000%, 7.100000%)]Attention! [/COLOR]When climbing or descending a steep section, the rack loco should always be on the downhill side of the train. Real rack railways follow this safety procedure, and LGB rack operators should abide by the same rule.
There are no special vertical curved transition track sections by any G-Scale manufacturer, maybe you could try to bend some yourself but the transition has to be fairly gradual.
As far as a turntable is concerned - at the top to turn the loco around.
I can't think of any rack railroad where this is the case, for safety reasons, the rack loco is always at the downhill side of the train going up and coming down.
Maybe look at some videos to get a feel for the prototypical operation.