1. No. The serpentine belt drives the accessories on the 'front' of the engine. The K series engine in both your Vs uses a timing CHAIN, not a belt. The chain doesn't need to be replaced routinely (unless you repeatably run the engine low on oil).
2. I replaced our SB at around 100K miles just for peace of mind. If you are doing it yourself, buy a SB tool like this one, it makes the job a LOT easier. Less than $20 USD.