Are they now charging to use the launderette? I was last on the ship in April and up till then it was free to use but if you didnt have any soap powder you could buy it in the shop or reception. The brochure or web site will show where the launderettes are on the various decks. I envy you. Say hello to Becky (from Grenada) in Magnums cigar/champagne bar for me. She is the driest and wittiest person I know and the best bartender.
Will take you to your deck simply move the box located mid ship to the left to see your mini suite. The only information is that is comprises of bewteen 370/560 sq ft but nothing more specific, perhaps you will hear from someone who has been in the suite. There is a 48 hour laundry service and a coin operated facility, but it can be noisy if you have accommodation opposite the facility but not in your case.
We stayed in a C deck aft minisuite on Sea Princess when she was Adonia with P&O. I managed to get the measurements of the various aft minis when we were booking. Your cabin, B748 is 365sq.ft. including the balcony of 6ft x 15ft 6" (large!). The B deck aft minis are not quite as large as the C deck ones but they are still lovely. They are completely different from the midship ones. You enter into a hallway where there will be a door into the toilet - there is another door from the toilet into the bathroom - very useful. If you continue down the hall the cabin opens out. Depending on which side of the ship you are - we were starboard - there is a wet bar to your right(or left if you see what I mean - the layout could be the other way round), past the wet bar is a TV and beneath it a fridge. Then there is the door to the balcony. If you imagine coming in from the balcony on your left is the settee, coffee table and two chairs. In front of you is the sleeping area, large bed and at the foot of it a dressing table, cupboards with second TV. On the right hand side of the bed is a walk-in wardrobe, door to the bathroom with jacuzzi bath and a set of drawers.
This is all assuming that nothing much has changed since she was with P&O. I don't think you get the extras in a minisuite with Princess that you do with P&O so I won't go into that. Hope this all helps. Let me know if you have any other questions. When she was Adonia we had an iron and ironing board in the wardrobe, don't know if that's still the case.