Practicalities
Getting things done in Galle is largely a social process. It is a small community where your reputation and your relationship with the people you deal with are critical. Conversely, it is important to find out about other people's reputation. It is generally true in Sri Lanka that reputation matters.
As we keep recommending on this site, get your information from the locals: you will usually find that the locals know everything the foreigners do, and a great deal more.
It is also important to be a little suspicious of recommendations for services. The British community in particular has a commission culture: many recommendations you receive will be biased expectations of a commission from the person recommended. We also recommend avoiding anyone whose clients are predominantly foreign.
Sri Lankan bureaucracy can be painful to deal with when you have to, but it is not a closely regulated society in terms of your personal life: you are only likely to need to deal with the government for visas, when buying property or building, and, if resident, to pay tax. Doing business is another matter.
You also need to be aware of some aspects of Sri Lankan law, both civil and criminal.
The biggest problems come from dealing with property and with day to day problems. Foreigners, in particular, are likely to be over-charged (at least).