I'm considering buying international RT J tickets for my wife and myself on Ctrip because the prices are about 20-25% cheaper than buying directly through the airline (likely UA). I know this comes with risks. I just want some assessment from anyone who's dealt with Ctrip before regarding how great the risks and hassles be:

1. Basically, we would use miles to travel SFO-PVG, then buy RT on Ctrip PVG-SFO-PVG. We'd travel on the ticketed date for PVG-SFO, then would change the SFO-PVG date later. Any sense of how much of a hassle this would be, dealing with Ctrip rather than the airline (again, likely UA), and what added charges Ctrip would add in addition to any airline rebooking fee and airline fee for additional ticket cost?
2. Same question as #1, except we might want to change to another destination for the return trip. Could be SFO to somewhere else in Asia, or even somewhere else in the world.
3. Any problems getting seat reservations via Ctrip?
4. I read in one thread here of someone's experience not getting any miles on a trip booked via Ctrip, but now can't find the thread. Any experience with this?

FWIW, the reason I'm even considering this crazy plan is that the RT price is cheap enough that if we didn't end up using the return SFO-PVG portion it might be worth it. But of course, if we could get some value out of the return trip it makes it definitely worth it.

Any thoughts or experience with this? Thanks for any help.