The installation isn't that involved. The implementation is a different thing depending upon how may different items are carried, how many states they do business in, and the number of different type of items sold.
To get things working correctly two things have to happen:
1) nexus is determined based upon the customer address. This means that each customer address has to be reviews and updated to make the format appropriate for Avalara to process. Fortunately, there is a batch process for this so it doesn't have to be done one at a time.
2) Each item in inventory (stock or misc) must have a tax class (probably have the term wrong) that tells Avalara how the item is handled for taxability. The list of codes was over 100 pages (2 columns wide) when we implemented internally 5 to 7 years ago.
For us, services had to be broken down between services provided with custom software, services provided with packaged software delivered electronically, services provided with packaged software delivered via media, services for on-going support on-site, services for on-going support remotely, etc.
The list is long because the differentiation is required by all the differences between states and localities. For example, services are taxable in Texas but not in Oklahoma. Services on implementations are taxable in Florida but services on support or follow-on projects are not taxable.
The process of analyzing the tax classes and the customers inventory and services is where there is a great opportunity for service revenue.
Happy consulting.