After the first horse, which is assigned, riders will select their own mounts from the line-up.
In the afternoons we will be turning the horses out again to graze and find water, and herding them back in as riders come in to the station. So, if you approach a ger after 12pm, there may only be a few horses on the line rather than the full complement. Those that are tied up should be freshly grazed and hydrated. This system will rely heavily on communications getting through seamlessly between urtuu teams warning each other when riders will be approaching the urtuu, and getting the herders to retrieve the horses in small batches and recycle the horses on the line.
It's conceivable that you could arrive at a horse station and there are no horses waiting due to a comms mix-up. You'll get the advantage of seeing your mounts being herded and get a good look at how a) fast and b) naughty they are. And they'll need less of a warm-up having been out for a leg-stretch. Chin up!
You are welcome to accept help saddling your steed and indeed getting back in the saddle, but you must take responsibility for the correct fit of your tack and your equipment on the horse. The herders will not have seen your saddles before and if their horse gets an injury from your girth rubbing, it's your responsibility. Check your tack before you get on and ride off.