Hi Gyves
Welcome to the campervan world. Not sure what engine is best, mine has the 2.4 115 tdci engine which is good but from reading on here some or the older engines as less trouble. Had mine for two years and no trouble yet (touch wood).
When I did my conversion I got a lot of the bits from Ebay, there are a lot of caravan / campervan suppliers that sell stuff on there so you can get most bits.
As far as the build, cant really advise as you want to take your stuff back out easily. My is built to stay as a camper so everything is fitted rigidly.
Its a lot of hard work but worth it in the end.
Have a look at the progress of mine.
http://fordtransit.org/forum/viewtopic.php?f=58&t=119763 been a few changes since but not uploaded any pics
