if you are going to simply add a custom barrel to a 700 action then the minimun you'll need is
go& nogo gauges
finish chamber reamer( can be rented)
there is an article at brownells site on doing this very thing to a 700..
barrels can be obtained from brownells , Midwayusa or barrel makers themselves such as Shaw(Mid-range barrel)
what you'll want is a 90% chambered barrel
you can pay what you want for a barrel( chrom-moly or SS)
there are many good books on re-barreling. Look at midway for these and READ them