First things you should do:
- engine oil
- gearbox/centre diff oil
- rear diff oil
- coolant
- spark plugs
This is the minimum on a car with unknown service history, and should be done as soon as you get your car.
As to the timing belt, you'd be safe (IMHO) to wait till 125,000 or more even.
You can tackle the timing belt yourself. There are lots of DIY guides online, some good and some really good. There are a few on the American forums which show step by step guides with pics too. There are also different tips which are really helpful.
You can get a kit from subaru for about 600 - just make sure that the kit comes with the tensioner and all pullies. Whilst you are there in the engine bay, you may as well change the water pump (not critical, but easy since your already working on that area of the engine.