I think their biggest challenge is that these Honor Guards do these well, but very few members have experience doing these state funerals as they happen so infrequently. IIRC, the last one was President Nixon's funeral in April, 1994. I also think that these Honor Guards aren't career positions but special duty assignments meaning that members rotate through frequently, usually two to four year assignments.
I'm sure that many former Honor Guard members are being mobilized to help and I'm sure many retired members with experience are being consulted to make sure everything runs smooth.