There should not be sparking if the tender wheels and the track are truly clean. Some other things to look for are first, good, clean contact between the brass axle wipers and the axles. Also verify the wheels are correctly gauged.
Second, specific to the 326 make sure the sliding pickups on the tender truck sideframes are clean, not worn out and the spring is keeping them in good contact with the rails. Also the axle holes can wear with a lot of use and cause the sideframe to rub on the rails which can cause sparking and shorting out at the turnouts.
I get parts at train shows. for mail orders PortLines is well stocked and reliable. Others use Jeff the Train Tender.
Parts needed depends on run time. Replacement bulbs are a must. Perhaps brushes but you need to know which styles are in your engines. The three you list should all be a shoulder style round brush; a few brush springs might also be needed. Next would be the replacement finger assemblies for the reverse units. I have a lot of other parts but all those are for repairs when I buy more items at train shows and fix them.
