First test if its a bleeder, cant express how important that is.....
If its a Pottery Barn type POS, just vac it really well set brown paper border for overspray, pretreat keep under 8 PH, prescrub with grady groomer, extract using ACID rinse, then groom shiny side up, I dont advise using the grady groomer for post grooming.
Never clean fringes in their house.
Use air mover to dry. A wool fiber has 3 parts to it, the outside is has scales that traps ALOT of soil and the inside is sponge like and can hold alot of water.
Cleaning wool in house will not remove all the soil. That rug may have a pound of dry soil in it.
Ask if they are anyone spot cleaned it, high PH spotter can damage the fibers, dont get blamed for someone elses mistake. They can loose their dye and stain much easier than nylon.
If you do end up doing act like you have done it a million times, the customer will know if you are unsure and then examine it even closer after you clean it.
Just be smart, some of those rugs are worth thousands. Most expensive rug I have cleaned was $26,000 dollars so the customer said.