loyal, i found this link on conversion kits for you:
http://www.currietech.com/e-conversionkit.html
this is the kit i use on my electric-assisted commuter bike (specialized hardrock). like i said in my post above, i've been pleased with it. really makes the commute fun, easy, and enjoyable.
one thing to note is, if you have a small-framed mtb, say under 19", you may need to mount the battery pack on a rear rack instead of the seat tube (as pictured elsewhere on currie's site). but this won't affect your ride - simply shifts your center of gravity back a bit.
in terms of your commute, it sounds like you can make a rt on a single charge, but if you find you can't, fast chargers (4-5 hours to full charge) are available for about $80 for re-charging at work. the kit itself does come with a charger - a slow charger (11-12 hours) for overnight charging.
the kit comes with everything you need to convert your bike (including directions). but unless you have an excess of tools, patience, and skill, well - i recommend taking it to a shop to do the install, or even locating a shop before you begin. there's a dealer locater on currie's site. that way you can test ride and also begin a relationship with the local electric vehicle shop - you'll be back for service eventually (unless you do it yourself, because of the electric drivetrain on the rear wheel, there are some procedures that only the e-shop will be able to handle for you).
-jb