The doo is easy to do yourself with all the guides out there. You'll probably be able to find somebody local who could help you.
As far as the oil, I assume you're talking about it burning oil at high speeds? That was more a problem for the '08's, but if it turns out that yours is burning oil it also isn't that hard to put in a 685 kit. Not something you would want to do for fun, but I didn't have any problem doing it following the online instructions, and before I bought my first motorcycle 6 years ago I had never even changed the oil before. These are really pretty simple bikes.
As far as using the KLR to commute, I had a couple. No problems at all. Rain--I commuted for a year in Portland. Cold--mine started in Iowa no problem down in the single digits. I don't think any bike you get is going to be the limiting factor in whether you use it to commute or not, I'm guessing you will be.