First off, if there's any jacking-up to do, I suggest you get a pro. What you might want to do for starters, is get an estimate for the work and ask the contractor if it involves jacking up the floor. If not, then you may be able to do the work yourself if you're confident you can do the job. Make sure you have him look at the sill, the ribbon board, and the foundation. THAT particular diagnosis will tell you if you have a bigger problem than you think.
Assuming you don't have to raise the floor, first and foremost, you need to get control of what caused the floor to rot. If the crawlspace is outside, it needs to be vented. (Approximately 1 vent per 250 sq. ft..) Next, if you have disfunctional gutters and downspouts, you need to correct them because water needs to be channeled AWAY from the foundation. (In the next rainstorm, get an umbrella and go outside to see how the water is running off the roof, in the gutters, and out the downspouts.) If you find water is 'missing' your gutters, and/or overflowing them, and/or pooling around your foundation, fix all the troubles. Assuming the 'system' is doing the right thing, if your crawlspace is inside and is dirt, you need to get 6+ mil thick plastic and lay it down to help keep moisture down. If your basement is smelling moldy or mildewy, consider a dehumidifier.
Now, further assuming that you've taken care of the source of the moisture, you can take steps to fix your joists. What you need to do first is 'coat' over your rotted joists with a sealant so the rot doesn't continue after you install new joists. (Ask the folks at the Home Center for a product for what you want to do. I don't have a brand recommendation.) Then, assuming your ribbon board can be nailed into, you need to get joist hangers for your new joists. (They're in the lumber section of the home centers.) Make sure you ask for the right TYPE of nails and right LENGTH. And put them in on a slight angle downwards. If the wood is slightly bowed, put the bow-side up. As far as how much room you need to work, a 3' crawlspace would be nice. Now, where do you put the joists??? Again, assuming your ribbons are good, if the 1st joist is 18" OC from the ribbon, put your 1st new joist 16" OC from the ribbon's OC, then go every 18". If you want to go every 16", go ahead.
This type of job may be bigger than you'd want it to be. BUT, you can do the preventative stuff w/the gutters, downspouts, and sealing of the old joists yourself. But from what it sounds like, your problem has gone waaaaay beyond where it should have gone. If you need to do some landscaping to KEEP water from coming back to the house, check the Forum for posts on French Drains and drainage and the like. You shouldn't need PT wood if you can control the moisture problems. In due time, PT wood can go 'bad' under adverse conditions.