Hi Vinny,
Praise the Lord for such a blessing!  If I were you, Vinny, I would not
worry about what I might not be able to do but concentrate on doing and
enjoying those thing I could do.  I believe this is a blessing given you by
the Lord and "whom He calls, he equipps".  What a blessing to be given, as
it were, a business.  I had to work many years to build up a business and
here you have a set of ready customers given to you.  Take it and run with
it!
There are a number of web sites where you can learn a lot of things about
action repair and regulation and you might get lots of help there.  Create a
network of technicians whom you can call on for advise and instruction. One
of the most important parts of the piano service business is customer
service.  A store I worked for for fifteen years always sent out reminder
cards once a month.  They only had something like a two percent response.  I
have always called my customers to remind them and to schedule them.  Most
of them really appreciate that and tell me many times how much they
appreciate me calling them so they don't have to keep up with it.  Keep good
records.  I use an old Dos program called Proffesional File.  It is a
database program and there is where my entire knowledge of my customers and
my business lives.  I also have the companion  word processor, Professional
Write.  I print orders or envoices and take them, fill them out, and leave a
copy with the customer as a receipt. I also keep records concerning the
piano and the work I did on it so that if there is ever a question, I have
the answer.  Also, I know the history of it's service and better able to
determine what it might need in the future.  If I can help you in any way,
feel free to write or, if need be, to call me.

Go for it!  God has given you a great opportunity.

Ned