First of all, I have never heard of Sherpa before, so I can't give you advice on that. That being said, here's my response to teh questions you asked:
I know very little about HTML and have never made a website. I do know how to make GIFs of my toons, but that's about all.
I am trying to decide now how to go about this. I see that you have sites like Keenspace, Comics Sherpa and Drunk Duck, which provide a pre-formatted web page. However, I kind of would like to have a more unique page.
Okay, this is kinda problematic. You don't know how to do HTML, yet you want a unique page - there's really nowhere this is possible, save for Geocities.

(They have a WYSIWYG engine) Keenspace gives you a standard page to being with, but to alter it, you need some knowledge of HTML and ftp, and I believe DrunkDuck is the same. A paying host will, as far as I know, not give you any kind of page to start out with - in that case, HTML is even more essential. Also, don't forget that Keenspace has the awesome Autokeen system which updates your comics and creates an archive automatically as long as you upload them to your FTP.
And I wonder if it isn't important to have your own URL, in order to be taken seriously (seriously funnily, I mean). Isn't having a URL with sherpa or keenspace in it, sort of the same as having a geocities web page? I mean, you are taken less seriously with those, both by people and by search engines, I would think. Am I wrong?
Y'know, people around here don't agree with that...

A lot of us are actually pretty proud to be 'Spacers, and plenty of good comics are on Keenspace. It's not all Megaman sprites. That being said, the vast majority of readers couldn't care less what your URL is - what matters is your comic! (though perhaps an ad-ladden Geocities site will scare people away...) By the way, I really don't think search engines take anyone 'less seriously' - if people search for your comic (or something insane - I got 'Corset template' this month), your comic will pop up, end of story.
I also have no idea how many hits I will get, and how much bandwidth I will need. I don't mind paying a little bit for a host, but don't want to be paying a lot of extra charges if I get too many hits.
How much bandwidth does the average online comic need?
This depends solely on how many readers you have, which again depends on how much you advertise and of course the quality of your comic. Sudden bandwith increases are one of the dangers of independant comic hosting - you never know quite how much bandwith you'll have to pay for untill your comic has gotten pretty established.
Do you think that Keenspace/Sherpa are an advantage to a new comic, or a disadvantage? Will being on those sites result in more people viewing my strip, or fewer?
Again, I have no clue about Sherpa, but in my opinion, Keenspace is definately an advantage to a new comic. The hosting is free, keeping you safe from sudden increases in bandwith cost, and there's a great and supportive community and some truly awesome admins. We're also certifically insane, which is always a plus. The only 'disadvantage' (since the servers are now very reliable, thanks to the admins), would be the 'Keenspace stigma' you mentioned, which I for one has never run into anywhere - and as said, if your comic is good, no one gives a damn shit where it's hosted.
I'd love to find a free or cheap host that will not only provide adequate bandwidth, but will also let me use my own URL. Any recommendations?
I this you know what I'm going to say: Keenspace.

The service and bandwith is free, you get Autokeen, plenty of community and promotion options (e.g. the newsbox), and if you really want your own domain, you can buy one cheaply and have it point to your keenspace site, and no one will even know that you're hosted on keenspace, unless they check the 'fine print'. Really, the only drawbacks about this option is that you have to have the adbanner on the top of your pages - but it's much prettier and less annoying than a Geocities banner, and if you went independant you'd most likely have ads to pay for the bandwith anyway.
... I think I should consider a job in advertizing.
