How long does it take to replace a CV axle shaft

Jack it up, slap a jacks tand under the frame, yank the wheel and zip the nut off the half shaft. Pull the lower ball joint nut and pop loose. Tap the half shaft through the hub, pry the other half loose from the transaxle (provided it's not a bolt together issue), pull the rotor away from the half shaft and pull the half shaft out of the way. Reassemble in the reverse order.
Course if it's one of those [Email]b@stards[/Email] that you can't remove the lower joint without first removing the cv axle (because it's in the way), you may have to disconnect the knuckle from the top side, however you have to do it. Just don't loosen anything up that adjusts alignment.
Just found a blown up image on google and if it's accurate, you should be able to remove the lower ball joint nut, pop it loose from the knuckle, and get enough clearance that way. Be careful not to damage the dust boot on the ball joint. You may have to pop the tie rod end loose as well and possibly hang the caliper somewhere else so the line doesn't limit how far you can move the hub out of the way.
Just realized you said anticipate the labor costs. I suggest calling around. Find out if it's cheaper to buy your own parts and bring them or have them supply the parts. Sometimes parts stores give shops a break on parts costs so the shop can mark things up a bit and make some money on parts as well as labor. I'm mentioning this because where I work, we get such decent prices on parts that when we mark them up, they often come in cheaper than what Joe off the street would pay just by walking into the same parts store. Some food for thought, don't automatically think the shop is ripping you off on parts.

It cost $90 in labor per side plus $70 for the shaft each total was around $390.00

I think book time is 1 hour.
Mopar warrenty times is something like .6 tenths

Sounds like your price is in line.

I have a frind with a shop,takes him about twenty minutes.

I bet he will charge the customer for more than 20 minutes! Its not about how long it takes, its more about what the job pays. Thats how technicans make money. Though sometimes it does not always work in their favor. Having the right tools and the know how is got to be worth something.

How quick they come apart really depends on where you are. I just had to change the front wheel bearing my my SIL's GMC 4x4. Never did it before so I googled it and there we a number of YouTube video's out there, all of them saying "you will spend hours with hammer, chisels,, gas wrench, etc. getting the old bearing out". Took my 15 minutes to swap them. I do not live where rust is an issue, nor salt.

I changed a number of CV shafts out in my 86 Daytona, similar to the Caravan's setup. I could do both in 30 minutes without having to touch the ball joints. Jack up car, pull tires, remove axle nut, smack end of axle stub with a hammer to pop it loose, crank the steering wheel all the way over (opposite direction from the side you are working on), pull shaft out, put in new, reassemble. Air tools though.

It'll cost whatever the flat rate says plus incidentals and tax. Call the service writer and he should be able to tell you TO THE PENNY what the charge will be. No need to guess.

I used to be upset at those $80/hr (now closer to $150/hr) labor rates until I thought about how much money I'd have to handle in a day to pay for overhead and insurance and a wage if I was in business for myself. It'll flat floor you when you think in those terms. And that's every day. There's no garage fairy doling out money to needy shop owners. Even the large auto dealerships stay in business by selling service.

So if you can't pay the time, don't do the crime. I do most of my own work because I can't afford $80 to change transmission fluid on a car with no changeable filter. Just drain and refill, $80. Five quarts at $6 a quart because it's an import using special synthetic was my total outlay. Changing 4 spark plugs and new wires on a DOHC motor with the plugs right on top? $150. Cost me $48. But my garage is already paid for and I have a fulltime job. Home labor pays $0.

Someone else mentioned knowledge and tools. That's huge. Take away either and you are looking at the possibility of enormous bills to make it right after you have boogered it up. Also, I am an engineer. What makes me twice as valuable as a kid fresh out of college? Experience and specialized knowledge that you don't get in school. That's all, but it's major.

Off my soapbox,
R.