I just relocated to the KC area myself 11 months ago. I too started my home search in the Smithville area and found out really quickly that it is extremely pricey there for what you get. Being that close to a big lake really drives up property values. Kearney is a good area, but tends to be a little pricey as well.
I purchased a home in the Lawson area and I'm sooooo glad I did. It's a great little community, homes are reasonably priced and you get way more for your money than you do in the other areas. The Lawson school system is great! My kids love it and there is an overwhelming amount of community support for school activities and athletics.
It's a little far North, but I don't mind it. I drive into the city every day, right down by the river on I-35 to work, and it's about 36 miles for me. A nice 45 minute drive in the morning to get prepared and have my coffee and a nice drive to wind down on the way home.
As far as getting your 6.4L worked on.......perfect area. I highly recommend Jason at Absolute Automotive. He specializes in Powerstrokes and was a Ford tech for something like 12 years. He is very reasonable on price and explains everything totally. Doesn't do anything that doesn't need to be done. There are a lot of rip-off diesel outfits in KC and dealers aren't much help on the diesels. I feel extremely fortunate to have found Jason. He is in the Kearney area and actually came to Lawson to troubleshoot and repair my 6.0L that wouldn't run.
Good luck on your home search. If you haven't found a realtor yet try Deanna Bradford at Reece and Nichols. She did a terrific job for us!