My advice is: Be concerned about foot care. You really dont want to come down with a bad case of blisters, given your medical history.
So Id prepare carefully, particularly regarding your footwear. You dont say exactly what the trip entails. Will you be backpacking? Doing long hikes in a single day, such as a down and up? Or part of a guided trip? Some slight variations in ideal footwear might be in order depending on the trip, but in general I think you need a midweight hiking boot that offers good support and foot protection (from thorns and rocks), along with good comfort.
You have lots of choices here. One excellent new boot that combines support with running-shoe comfort is Montrails Stratos XCR Hiking Boot ($140; www.montrail.com). Its a mid-height boot that doesnt come up quite as high as a regular" hiking boot, but it will still cover your ankle bone. Its very light (just over a pound), with a well-padded EVA midsole. I can take or leave the Gore-Tex liner, but on a spring trip you might be doing some stream-hopping, so it could be useful. A similar boot is L.L. Beans well-priced GTX Mountain Treads Mid-Cut ($119; www.llbean.com), with a mid-height design, waterproof liner, and midsole built like those found on trail-runners. Provided you have a good fit, either the Stratos or GTX Mountain Treads offer near out-of-the-box wearability.
If you want something with a little more heft, then consider Scarpas mostly leather ZG 40 GTX ($159; www.scarpa.com). Ive always like Scarpa boots, and these offer the protection of a full-height boot with a lot of weight (nearly three pounds). They also have a Gore-Tex liner, which may not be ideal for a hot-weather hike, but theyre breathable, and you may appreciate the waterproof protection if conditions are sloppy.
Finally, for a classic all-leather boot, take a look at Garmonts Dakota ($249; www.garmont.com). Its one-piece leather construction is inherently water-resistant, while offering plenty of support and durability. This is the boot if youre planning on carrying a load over multiple days. Just take the time to break them in with local, short hikes. Then work your way up.
Whatever you decide, make sure you fit them carefully. Wear good socksa wicking liner made with CoolMax or polypropylene is advisable as well as an oversock, such as the SmartWool Light Hiker ($12; www.smartwool.com). And take some time to wear them on several warm-up trips to ensure you arent developing hot spots.
And train carefully for the trip. The Grand Canyon is an odd duck; you start out with the EASY part, the downhill. Many is the hiker who has happily switchbacked down into the deep, only to look up after an hour, legs slightly rubbery from the downhill pounding, and said, Oh, darn!" Or something else that shouldnt be repeated here. Combine that with the Grand Canyons elevation (the canyon rim on the south side is around 8,000 feet), its potential for heat, and its aridity, and youve got a challenging hike. But the scenery! Ah, sublime.
Read GORP.coms Ten Easy Steps to Happy Hiking Feet" for more info on healthy peds.
Also, check out this years more than 400 must-have gear items, including a comprehensive boots section, in the 2006 Buyers Guide.