If you are somewhat handy, you should be able to do it yourself. I had the same problem in a former vehicle and was able to replace the defective part in under an hour... most difficult part was getting access to it.
Hopefully someone will chime in with more knowledge, but I believe the part you need to replace is somewhere behind the glovebox above the front passenger footwell. It should just be a couple of bolts and one connector once you know how to access the defective component. I don't believe you'll need anything more than some basic hand tools. IIRC, the part should only be around $30 too. Here is another thread from another board member with the same problem:viewtopic.php?f=8&t=9666&hilit=blower+motor+resistor
Finally, here is a thread for a TSB for replacement the blower motor resistor in Hybrid models. viewtopic.php?f=24&t=1236&hilit=blower+motor+resistorNOTE:
I believe all 2008+ Hybrid models came with EATC (Electronic Automatic Temperature Control) which your XLT does not have. Therefore, the part numbers in this thread are probably not correct for your application. However, I would imagine that the location of the blower motor resistor is the same between Hybrid/ Non-Hybrid models.
If I were you, I'd pull the old blower resistor out and get the part # off of it to be sure I was buying the correct replacement component.
Hope this helps.