We used to self clean our carpets also. When we got new cut pile carpet we were advised to use only steam methods. It is better. There is no soap residue which holds on to the dirt, IMHO.
Be warned, they will try to sell you all kinds of stuff during the visit. We have 2 cats, one big messy dog and two adult sons living with DH and I. I know about dirt and messes. DH had them do the 'scotch guard and deodorizing' treatment to the tune of an additional hundred or so. It didn't make any difference at all. The house doesn't smell, even with the cat boxes cause we keep them squeaky clean.
I did buy the spot remover spray and it is really worth it. We use Stainmaster and I have been pleased with them and the spot remover.
Word of caution, I am missing a couple pieces of jewelry. I have no idea if the guy who was cleaning in the bedroom while the other guy was trying to talk me into the extras is responsible and when it even happened. I don't have a dresser top jewelry box but one in my armoire. I now put anything of value like electronics, jewelry and medicines in there and use a small zip tie on the knobs. Anyone could open it by cutting the tie but they couldn't deny they had done so. I hate having people come in. I have never had any problems except for this. How can you prove who took something?