How long should it take

It depends upon the availability of electronics and wiring harnesses which have to be custom made. My brother did one on his own in his Warlock in his garage with no lift. Made custom exhaust and changed to a manual 6 speed from a Viper. He had most of the stuff before beginning but waited on a harness for a while. I think it took him two months of working after his day job. It should take a shop less than a month if they have everything they need. It's not a drop in, so expect some delays and extra fabricated parts.

Cost? New Hemi? Used? You supplying the motor or are they? I think my brother spent $1500 on a 2009 5.7 truck motor with 100K miles.