To answer the OP's initial questions.

I found ukulele relatively easy to get started on. Most people I've come across have been able to achieve sufficient basic competence to be able to play simple strummed 3 chord song accompaniments in a few weeks. From there it's a matter of where you want to go. It's a serious musical instrument and can repay a lifetime's study or it's an instrument you can pick up and put down for your own pleasure and play a pleasing sounding accompaniment.

As other's have said Artful Codger has provided some useful advice though I disagree with some of it. I disagree with his arguing against the soprano. That's a matter of personal taste. I like my sopranos but, contrary to popular belief, hand size doesn't really come into it. I've come across people with great big sausage-like fingers happily playing soprano ukulele. It's true you need to be more careful about finger placement and there are more likely to be intonation issues but proper setup should deal with the latter. The former is a matter of practice.

Secondly, though a strap is useful, and with the larger sizes getting near essential, I would avoid the uke thong. The idea of hooking something into the sound hole makes me shudder. Too much possibility for damage. Much better to pay to have strap buttons fitted. Alternatively, investigate the uke leash. (http://ukeleash.com/) That's what I use. A strap which loops round your upper arm and attaches to the headstock. It gives enough support to the left hand to leave it free to move between chords easily. My banjo uke is heavy and I use an actual banjo strap for that, so it does depend.

I've mixed feelings about the capo. It's a useful tool but I find it gets in the way. Like most ukulele players I own several ukes and use them in different tunings instead.

I would add Hawaii Music Supply (http://www.theukulelesite.com/) to the list of suggested shops. They have a stellar reputation and properly set up every uke they sell. I've not used them myself as I'm in the UK but they are uniformly recommended on the ukulele underground forum.

When I was starting out, I found "Got a ukulele" site very useful (http://www.gotaukulele.com/) and he has a couple of useful books which add extra information not found in tutor books.

Look up "Uke Minutes" on You Tube. Short tutorial videos from basics upward. Aldrine Guerrero who produces them is a well respected ukulele player who knows what he is talking about. Possibly better than many lessons.

I also recommend joining the ukulele underground forum. It's a mine of useful information and has a beginners forum: http://forum.ukuleleunderground.com/

Finally, don't let anybody tell you you must do this or you must do it that way. It's your ukulele and you know what you want to get out of it.

Enjoy the ukulele