Just kinda guessing by your goals and requirements here, but doing your own budget turbo kit might well be the way you should go. You can do it on the cheap with research and some elbow grease. If you are willing to take the time to do it, tuning is really the only thing I see you not being able to DIY. Assuming you the 4 bangers use the same JTEC ecu, you could probably find someone to do that for you.
If it were me and I was planning to turbo my '98 4 banger, I'd start off asking around about tuning specifically your rig. Then determine what injector upgrades are available (do they just use the same as 4.0s?--if so, that's easy). I would assume the fuel pump is the same which should be plenty for a small turbo. Then you need to figure out how to mount a turbo and route all the intake/exhaust piping. You'd have to spend some time looking up his other people have done custom turbo installs, but it's all basically the same while all being custom fit. A water/air intercooler setup would probably be easiest to package but there's more plumbing involved. Turbo selection is the easiest part of it all.
How is your welding?
If it were me and I was planning to turbo my '98 4 banger, I'd start off asking around about tuning specifically your rig. Then determine what injector upgrades are available (do they just use the same as 4.0s?--if so, that's easy). I would assume the fuel pump is the same which should be plenty for a small turbo. Then you need to figure out how to mount a turbo and route all the intake/exhaust piping. You'd have to spend some time looking up his other people have done custom turbo installs, but it's all basically the same while all being custom fit. A water/air intercooler setup would probably be easiest to package but there's more plumbing involved. Turbo selection is the easiest part of it all.
How is your welding?