Horrible board - how to oust, if possible

Read your bylaws regarding calling a shareholder meeting or when the annual meeting takes place, make sure to get a quorum and the proper amount of votes/proxies in your favor to oust the board (usually a majority or 2/3rds), and elect new members. If they are really bad and breaching their fiduciary duty, you can bring a shareholder derivative action - but I don't think you want to go down that road just yet.

would the managing agent have the bylaws? ideas on how to do this in stealth mode since these people would still be neighbors?

Managing agent should have the bylaws - so should you, though. Hard to do this in stealth since you will need to solicit all your neighbors to either vote with you or give you a proxy. You'll also need to solicit new potential board members to run against the current board. Finding people who are not only qualified to run a building but willing to do this, may be tough.

Most boards hold annual elections. That is the "in" I used when the board at a coop I used to live in got out of control with spending and irresponsible with the number of capital projects it undertook at once. I gathered a slate of people who as a group brought various skills: (1) long historical knowledge of the coop because of long residency and past board participation; (2) finance background; (3) legal skills; (4) accounting skills; (5) engineering and construction knowledge; (6) ethics and compliance knowledge; (7) negotiating skills. As a group they had everything an effective board would need. We built support in the building leading up to the annual meeting by each meeting with residents one-on-one and explaining the ways in which the current board was unsatisfactory and the ways our slate could address those problems and turn things around. I also coordinated each candidate creating a bio and statement explaining his/her reason for running and particular stregnths which were distributed in advance of the meeting. We conducted a successful campaign and by the time the votes were counted, our candidates resoundingly won. We avoided personal attacks of any type and focused exclusively on issues. My point: you don't just run people you think will do a good job and hope they win. It takes a considered strategy, time, effort, and a real campaign to increase the chances of success. If there is truly a need for change, then others should see it. If they don't, then maybe you have misjudged the job the current board is doing.