Aha Hollister stuck on....you are ^^ Well at the start Hollister will be throwing dynamite at you, so get your shotgun out go over to where he is, shoot him (if you don't do mich damage as you said you havent done many side missions then i suggest you use Quickdraw alot to!) and then he will get his shotgun/rifle out and chase you. To do this level i ran until i found a decent sized rock to hide behind, one where u can still see where he is but where he carnt shoot you. What i did was quickly move to the side of the rock (slightly) so he shot but move quickly in so he misses, as soon as he shot i would run out and shoot then hide again. If you don't choose this technique then whenever he fires at you if he misses or hits fire back straight away because he carnt fire 2 bullets side to side, fire back straightaway then hide, repeat this then eventually you will get his health down about 3/4 of the way and a little video will come on , he is strapping dynamite to himself, now it gets easY! he will chase after you with dynamite strapped to him, just run and after about 15-30 seconds he will blow up woot!
Sorry for such a long explanation :p