maybe I opened a can of worms......

I called the LBS they told me that the wheels are true and the bike needs hub service, there is a grinding and popping when the wheel spins. They said 75-100 for a new wheel. even more to replace the hub. He said that is if get a new set of wheels and run a shimano cassette (which is what the wheel takes that I am looking at) it might not work because I have suntour components (it currently has suntour cassette) since it was meant to have a suntour. Someone who has experience with this help me out. It doesn't pay for me to get the new wheels, spacer and cassette if it it not going to shift and work? any info would be greatly appreciated