To be perfectly honest, yes. The Longstrike, along with the other original N-Strike blasters with the reverse plungers, is severely limited in the upgradeability department. There have been plenty of people whome have been able to replace the original reverse plungers with donors out of Retaliators, which is what the OMW and Xplorer sets are designed to emulate. It takes some work, but definitely improves the performance. Personally, I think that ordering the kits is the lazy way out.
I have no proper tools at my disposal, the current modifications I did almost destroyed the internals because of the tools I used, which is why buying is currently the better option for me.