Some of the jobs like this are not so cut & dry to answer, if this is a steady customer & he is determined to get the face re lettered, he will find someone to do it & you could lose the customer, also it depends on how much work you have, if you charge for r&r the face with a truck, remove the vinyl, clean the face & re letter it, there is not a lot of out of pocket cost involved, if you would have been standing around sweeping the shop, you are ahead of the game, if you want to do the job, explain to the customer when you take off the vinyl, there will be ghosting, then scrub the face with SOS & soft scrub with bleach & hose it down, letter it upside down from the old lettering & you should be fine. As long as there is not too much ghosting, which I have not seen yet.