Should you DIY? Depends on the siding type, complexity, difficulty of install, house elevation (are you going to spend more in scaffolding than you would paying an installer?) and possible warranty implications (some siding mnfgs will warranty diy siding others not). Hard question to answer at this point
As for types, personally I'm fond of the "fiber cement siding" if you're looking for a "do it once and its done" siding imho this seems to be the stuff. Failing that either Western red cedar or redwood would be my second choice durability wise.
I had some sort of paper mache stuff (the pressboard and glue precursor to the fiber cement) on the last house (subject of several class action suites and settlements) so am perhaps a big gun shy on the various "fiber board" sidings like T-111 and the like (I know they can be ok but they're fussy to install just right and knowing if its a good type seems difficult).
The fiber cement can be DIY, but its heavy and because the boards are so long they're kind of fragile until they're in place so two people is a LOT easier than one and there are some installation tools that make alignment much easier. You also have to be careful about proper installation since over or under tightening the fasteners can dramatically affect the expected lifespan/durability of the install.
The other consideration against (or maybe for depending on the quality of contractors in your area
) DIY is that the devil is in the details (in response to your question about trim). Just putting up siding isn't to hard but getting the vapor barrier properly installed and all of the trim in the right places in regards to it (especially around penetration points like windows) so that water is properly drained away from the house is a wee bit of an art.
There are some really good guides out there though:
To start with browse through the jlc guide:
http://www.jlconline.com/building/exterior/siding-and-trim/
at least thier best practices videos:
http://www.jlconline.com/exteriors/best-practices-from-jlc-live_o.aspx?dfpzone=building.exterior
This is worth it imho even if you outsource because its nice to have at least enough knowledge to know if the contractor is doing it right
Also when you have the siding off is the time to check your insulation and energy barriers as well
I may be weird but I enjoyed reading this book and it paid for itself fairly quickly (I got it used):
http://www.amazon.com/The-JLC-Guide-Energy-Efficiency/dp/1928580467