Okay, deep breath......... you still have two weeks left to find out the answers to all your questions!
Getting hold of a good guide book is an excellent start, and asking as many questions as you like on these boards is another sure fire way to get some answers.
I'd suggest starting a new thread for each question - that way you're more likely to get some replies and it's easier for people to answer one specific thing at a time. that said, I'll have a go at your list!
Originally posted by R1-IAN
what do we need to do when we land there,never had a hire car before on holiday....
Are you flying to Sanford or Orlnado International? If Sanford then it's very straightforward - you clear immigration, collect luggage and then head out of the door to the Car rental desks.
If International, it's more complicated (and I hope I've remembered this in the correct order!). You clear immigration, collect your luggage, go through customs, put your luggage back on a conveyor belt and board (luggage-less) a monorail to the main terminal building. Then you find your lugagge all over again and
then you go to get your rental car. Some of the rental desks are in the main building, some require a short bus ride from the airport on a shuttle. Do you know where yours is?
If you're flying with Virgin or are on a tour operator package trip, there are plenty of representatives throughout the baggage reclaim areas to help you find your way and point you to the right areas for everything.
what money will we need for the toll booth.....
If you can have some small dollar bills it will make life easier. The tols are somewhere in the region of $1.50 each, and you'll go through two or three to reach most of Orlando / Kissimmee. Simon's Brit's Guide gives you more detail if you can get hold of one before you go.
how easy is it to find your hotel......
Some of the tour operators / most of the car rental desks will give you maps to help you find your way.
Make sure you know the address of your hotel, not just the name - there may be several hotels with very similar names
money do i take it all in US t/cheque or take some in UK t/cheque
Most people here seem to take some t/c and some cash, as well as using a credit card if you have one.
Take US t/c not UK US tc can be used just like cash in most shops/restaurants. You won't want to be looking for somewhere to change your sterling tcs in the middle of the parks! Credit cards can work out slightly cheaper on the exchange rate (varies form card to card), but you need to keep an eye on what you're spending!
will £3000 be enough
That depends on what you plan to spend!

Have you already paid for park tickets, car hire? It sounds a lot for just two of you IMHO, but everyone has a different view.
Ian