You're quite insane. Fuggetaboutit. Stay home with brats and beer. <img src="/forums/images/graemlins/grin.gif" alt="" />

But seriously, given your backround, the area and the time of year your plan sounds reasonable.

A few random thoughts:

That area of Yosemite in late July will be very crowded. Are you talking the JMT or another route perhaps through Merced Lake? Either way you'll need a permit for an overnight trip. Walk in permits are available first come first served but they are not guaranteed. Permits can be reserved in advance but as you can see here quotas fill very quickly. At that time of year on those trails you stand a pretty good chance of being stopped for a permit check by a ranger. But the upside of all the crowds is this: If you do run into trouble and you're solo help could be very near.

You'll definitely need a bear canister. Required by law.

Tuolumne to the Valley involves a significant elevation drop. That much downhill walking can be very hard on the knees and the quads. Now add the weight of a 4 day pack to the equation. Prepare for that. Even if you're 26.

You mentioned a lot of activities over a long period of time but you really didn't specify your fitness level. Weekend day hikes may or may not be enough at this time. Train the same way you'll hike.....with a loaded pack on. Condition your back and shoulders as well as your legs. Backpacking is very different than day hiking. Check out some hiking poles. Lots of folks here swear by them.

You'll be at altitudes far above anything the Midwest has to offer. It's really hard to train for that so just be prepared to compensate your pace a little. And you won't have that Midwest summer humidity. The Sierra air is usually very dry. You'll be sweating much more than you may notice. You'll also be hitting the area during thunderstorm/lightning season but I'm sure you're used to that.

Be familiar with your camping equipment. I always tell people to do a "dress rehearsal" with exactly everything you'll carry on the real McCoy, but just spend a night car camping or even in your back yard. People new to backpacking tend to take way too much stuff. Fire up your stove and cook a few meals to determine how much fuel you'll actually need. Learn what you can live without in your back yard before you leave. Your legs will thank you during that last long descent into the valley.