The other "h." جنيه Sorry, my transliterations tend to kind of suck.

Piastres are قرش ... so hey, a ج and a ق for you all in one go.

No one will look at you askance if you use standard over local pronunciations, especially given a foreign accent ... that you know how to say anything even remotely comprehensible at all will delight people to no end. I'm guessing it was pretty much the same story in Morocco? But yeah, the "j/g" thing especially repeatedly threw me for a loop in understanding what
other people were saying ... many times I found myself staring completely blankly at someone who was in fact using a word I knew perfectly well. You wouldn't think it would matter so much, but if your language is shaky to begin with ... oi.
Clothes-wise ... you
can wear whatever makes you comfortable. Even off the beaten path, it's a country that relies on tourism ... people aren't very shockable when it comes to foreigners. And even more urban local fashion, unless its changed dramatically in the past few years, encompasses a lot of skin tight clothes and even some room for the occasional short skirt, tube top, or whatever, so just normal, comfy, non-flashy clothes will get enough respect even if they're not offering coverage up to the topmost local ideals.
The closer you get the the ideals, though, in the broader population the more social perks there are for you. I know of several people who just by my nationality had some pretty awful preconceived notions about me, but the very second they saw me it all turned to "oh my god, she's a walking angel." On a deeper level it's actually kind of troubling, but superficially it's a very convenient way to make a lazy good impression. An abaya would win you those cultural brownie points if you wanted to visit the Muhammad Ali mosque in Cairo, Azhar, or maybe the Mursi mosque in Alexandria, though at least in the bigger ones like those it's not really required. (They're used to tourists too.

AFAIK they tend to ask visitors to wear long trousers or skirts and at least some kind of sleeve.)
But in short: whatever balance works for you, go with it.
