Hi Gillbo
I did this trip in March last year - it's an amazing place, you'll have a fantastic time.
If you put 'Icelend' into the search function at the top of the page, you'll find reviews and tips from myself and a number of my fellow travellers, including Bob Gray, which should answer most of your questions.
Top tip is to pack layers and bear in mind that you will be on and off the coach quite a bit so wear stuff you can throw on and off easily. The Hotel and restaurants are also warm and comfortable so you won't need to walk around dressed like the Michelin Man once you are inside! Don't bother to take a brolly because it's so windy that you will never keep it up and the locals will give you a look of distain for even trying 🙂
Happy to help if you have any other questions
All the best
Mandy