I like my action somewhat low, but not so low that I get buzzes, with my American P-bass I have the action at the 17th fret set to about 2mm for the E string and ~1.6mm for the others (slightly lower for the g string).

I've always been a DIYer, so I do it myself.

Bass guitars are really quite simple and as long as you don't go ape on it then it should be pretty easy to figure all this stuff out, especially with all the information available out there.

For a basic setup you really just need to adjust the truss rod if applicable, adjust the action and adjust the intonation, and perhaps adjust the pickup height, and of course tune the instrument. All of these things are very easy to do, especially if you are very methodical and you have the right tools. For example, don't just eyeball the neck for truss rod adjustments, clamp a capo at the first fret, push down on the last fret, then use a feeler gauge at the 8th fret to measure the relief (ideal neck relief will depend on your neck radius).

Don't be afraid to setup your own bass. It might be intimidating, but it's pretty hard to do permanent damage unless you go completely primal on it. Just educate yourself by doing a little research and don't rush things. Use the right tools for the job, most tools can be had for very cheap. However, if you get to where you want to build nuts and do nut adjustments then don't cheap out on the files, but nut adjustments are more advanced and not a part of a basic setup and it's probably better to take it to a luthier in this case because you'll spend a lot of money on tools for a job you might do only do a couple times (unless you make it a hobby or side job fixing guitars).