You have a few options...if you had a pic I could lead you in the better direction.
1) Rent an overseeder from your local rental yard. Landpride offers a 48" unit that mounts on your 3 pt and is powered with your PTO. There are vertical blades in the front that slice the ground, then seed drops in behind, and finally a cultipacker in the back that rolls the seed firmly in place. With this unit you would just go over what you have now. Two passed perpendicular to each other. Typical rental charge is $200. This would not fill in your low areas. But you could bring in some topsoil and spread with your loader?
2) Again rent or purchase a rototiller and landscape rake (with gage wheels). If you have a lot of rocks though, this option may not be the best. The rototiller will take a beating.
3) Go the old farm way, buy a moldboard plow, disc, and some type of harrow drag. You can use these items every year for your garden as well!
4) Lastly and probably the best tool by far is the harley rake. New these are $6,000. Again you should be able to rent one for about $250 a day. Awesome tool, 3 in 1, replaces the rototiller, box blade and landscape rake. Go over a couple times for your rough pass, then angle it and take a light skim pass, you will have a perfectly smooth seedbed. It will windrow any and all junk (rocks, stones, sticks, etc.) off to one side for disposal.