Dave,
Yes, you can do the installation yourself, but if there is a good quality, i.e., been in business for 25-30 years, I would ask them if the installation includes facing the headtube and squaring the fork crown, and if it does, what the cost will be? These things are important (especially on old French bicycles which were probably not prepped in the first place!!!).
I'm from the school (my father!!!!) which accentuates "proper" tools, but you can be creative with bicycles (to a point) and have a feeling of satisfaction. The main thing is check out the bike shop, because if they are "top shelf" it might be best to let them do the job....just beware of "cobblers!!!"
Chuck Brooks Malta (temperature dropping approx 30 degrees tomorrow) NY