Best is buy the part from workshop and take to mechanic. If you are in Klang Valley I can recommend good mechanics and part shops.

Viva has a tough engine and you only need to service those 'sacrificial' items (bearings, belts, mounting etc).

Water pump no need to change. My Kelisa of 15 years still haven't change water pump. It uses a steel impeller directly driven by the belt so it's very unlikely to fail. Some other manufacturers use plastic impellers so ppl sometimes recommend you change it. Daihatsu doesn't have this issue.

As long as you keep an eye on the car, most hoses only need to change if leaking.

8 years is a good time to change mounting (engine and gearbox) but bear in mind both parts and labour is expensive. Changing them will reduce vibration and improve handling and engine response. In the long-term it also reduces stress to your subframe.

For spare part I usually go to Bay Brothers in PJ., near Hilton. They are quite big and supply to many foreman. Then if you go to the back of the shop there is a row of mechanics who only do labour, so you definitely save there. They look kinda unprofessional but they have been servicing taxis and other high mileage vehicles for ages already. For this reason they are quite reasonably priced and very efficient. Have sent newer cars there for complex jobs with no issues.
Been going there for close to 20 years with no complaints so far.