Easter in Hungary and Czech

1. Yes. Though the exchange places will rip you off. Use an ATM where possible.
2. Er, a train might be a lot more convenient and you can admire the views.
3. Yes if you use the motorways/highways in the Czech Republic (and probably in Slovakia and Hungary as well).

Thank you Jeremy.

Actually, there are many moneychangers in Prague who won't rip you off. Those advertising their rates in big digits on boards outside their office definitely will ... The trick is that those big numbers are selling rates, the ones used if you are buying foreign currency from them. A honest business (e.g. Exchange.cz) will clearly indicate buy/sell rates.

Highway "stickers" in Czech Republic are sold at petrol stations and the 2012 prices are 310/440/1500Kc for 10 days/1 months/1 year. You will definitely need one if driving from Hungary to Prague.

Stickers:

Hungary: there is so called electronic sticker - you will just a fill a simple form at the petrol station and pay and your car plate will be recorded in database of cars "eligible" to drive the highway (checked by Big Brother cameras). Keep the receipt to show it on demand.
The price for 10 days validity is 2750 HUF, what is about 9,5 EUR.

Slovakia: you need to buy sticker, the cheapest one is 10€ valid for 10 days. You can buy it already at the petrol station in Hungary or on the border crossing so you will enter Slovakia with it.

Czech republic: you need to buy sticker, the cheapest one is 310 CZK (approx 12,5 € ) valid for 10 days. You can buy it already at the petrol station in Slovakia (maybe even already in Hungary) or on the border crossing so you will enter Czechia with it.

By the way, I would also recommend train. It takes about 7 hours from Budapest to Prague and you need no stickers :-) (so you will save about 30 EUR for stickers and the environment would thank you :-)