You'll need to remove the preset trimmers from the PCB they are installed on (I seem to remember you have to desolder all wires coming to the PCB, make notes before doing that!). Then, very carefully pull the plastic thumbwheel off the metal axle. Spray a little contact cleaner or isopropanol on the axle and inside the trimmer, then carefully work the axle with pliers. It should come loose and start working nicely after you've turned it end to end several times.
Finish off with a tiny amount of lubricant on the axle (I think I used white lithium grease - don't get that on the actual carbon track inside the trimmer) and it's a good idea to lubricate the still working trimmers as well. Push the thumbwheels back in place and they should still have enough grip to turn the preset with no problems. If not, epoxy might be the answer. I had to free 9 of my 10 presets and all ended up working fine!
Do all your dial & marker lights work? It's a silly circuit and needs the exact right bulb values to work properly. I believe Dillen can supply these if need be.
Re: the sticky dial, you'll probably also need to clean and lubricate the metal rod that the dial pointer rides on.