Originally Posted by cpach

You can replace the shifters with anything cross compatible with 3x8 Shimano, including Shimano, Microshift, and Sram shifters labeled for the 2:1 ratio. 3x8 shifters tend to work pretty well even at relatively low price points. Truthfully even relatively low end brake levers and linear pull calipers rarely need or warrant replacement, and you can probably get very good performance with your braking system if you clean and lube the pivot points, replace the cable and housing, and replace the brake pads. If you do want to replace your braking system, you may want to just get some Shimano brake/shift levers to save on cost, like Shimano ST-EF500. For brakes, Shimano is again a pretty good source, even their least expensive brakes you can easily source as a consumer are totally fine, like BR-T4000.

As an aside, have you checked your chain for wear? Sounds like you have some good miles behind you. If you don't have a chain checking tool, you can very carefully use a ruler to measure 12 links. At 12" it's new, at 12 -1/16 it's time to replace, at 12 - 1/8 your whole drive train is worn. If your whole drivetrain is worn, but everything shifts fine, it can sometimes make sense to run everything into the ground, then replace the chain, cassette, and chainrings (or whole crank, in lower-priced parts) together.