Invoicing Programme, b2b interface

I´m a mac user(have been for 14 years) and know NOTHING much about pc´s:-(
Want to start a new business, but need an effective and professional(Not necessarily complicated) invoicing system, where hopefully,I can invoice my customers professionally and am am able to keep a record of all their previous purchases. At the moment, my options are, an ancient Filemaker pro Mac programme, or emailing PDF invoices created in XLS, which look like a sack of shit !!
Also, need "something" creating, that my customers can log on to with a password, and place their orders with us via an easily managable system.
Remember, this discription is being written by a PC Dummy of the highest order.
I need to bring my IT system in line with my customers, who obviosly use PC´s.
I need an easy solution to this. Someone who can load the whole lot into our office PC, so I can begin to use it immediately, without a 4 year traing course !!
I need to know;
1.What is possible
2.How much you will charge me to do it.
3.Do I have any options (apart from pouring petrol onto my mac and setting fire to it!!!).
I live in Randers and can be contacted on sales@foodfromhome.dk