Long size fragments cloning

[Luc Ferrari]

Hi,

we are actually sequencing a long size fragment of DNA, from a cosmid 
library. We have several problems. I hope we could find help here.

Is the size of the vector (plasmid) in relation with the size of the DNA 
insert ?

What plasmid could we use to insert a 15kb DNA fragment ? (I said long size)

What is the ideal transfection methods for such a plasmid, and in which 
bacteria could we transfected it ?

Thanks for e-mailed answers.

Luc