Hi Rich, and welcome to the forum
The major determinant of cost is volume - at a rough guess you are looking at £5-10,000 for your possessions by container(s), then, of course the cost of getting you all over
you have then got registration tax to pay on the vehicles, which can go into the thousands, but if you've owned a car for over 2 years you maybe exempt (one car per person I believe)
As for how long, as Malta is in the EU, then assuming you are EU citizens then the paperwork is fairly straightforward, and can all be done on arrival - you have the right to live and work in Malta.
The following is a good place to start
http://britishexpat.com/expatforum/malta/viewtopic.php?t=8544
covers
1. An EU citizens legal rights - residency, working, students
2. what sort of residency is available ?
3. what do I need to apply for if I want to reside in Malta ?
4. do I need to apply for residency before coming to live in Malta ?
5. do I need an accountant to apply for residency ?
6. do I need health insurance ?
6.1 Do I qualify for public health cover, and if I do, what cover do I have ? Are prescriptions free ?
7. can I work in Malta ?
7.1 How much is income tax ?
7.2 How much are social security contributions ?
8. where do I apply for my residency certificate ?
9. where can I get the OR application form ?
10. where do I apply for my ID card ?
11. what documents do I need to apply for OR ?
12. can I vote in Malta ?
13. buying a property FAQ
14. renting a property FAQ
15. Importing a vehicle FAQ
16. What's the procedure for importing/exporting a pet ?
17. Can I use my driving licence in Malta ?
17.1 Applying for driving licence
18. Long term residency certificate