What upgrades should i do to my 98 civic ex?

stay away from the ebay crap. Also what do you want. If you want it to be faster, sell off all the stereo crap you just bought, and gut it rip out all the sound deading material, back seat, carpet plastic trim, everything, Lowering springs will get you nothing other than blown shocks. The Skunk2 Pro intake is a good option, as is a adj FPR, or a slightly bored out TB. Stick with a 15" rim, or your handleing will suffer. Good high quilaty shocks will run about 15oo for adj coilovers. Go with Pword JDM traigulated strut bars. If you can get a K swap for 2K you are a lucky SOB, They run more like 5-6K complete. a lightly modded B will run you around 2k and will basically double your power. If you really are serious about this look into the big boys. AEM, Moton, Skunk, Bisimoto, EXOSPEED, Crower, Hondata, Spend the time and do the research. You have to remember HP=money. plain and simple. But if you really want a motor swap look into the 3.2L v6. If it will fit in my EG HB it will fit in your 98. Also it is header not headers. you only have 1.