Picking up 4 stars as an enginer is quite easy as well (easier actualy as an engineer is esential in nearly all maps).
Learning to snipe is tricker and I get frustrated as I can shoot better in real life than I can on the FPS games. You can make up for it by stealing pants.
Field ops is another that is not too hard to rack up the points if you are playing against a team that likes to clusterf4 together. Just drop some arty on them and you have an instant 4 kills on one shot.
As for being a battle medic, I think that as long as you remember that your prime task is to care for your team mates. I have no issue with a medic mixing it up unless they are whoreing points at the expense of team members that need reviving or health packs.
It is tactialy advantageous to get as many stars as early as you can as a medic so you can have full revive, and super health packs. Again it's the team work thing.
All that said and done, remember the motto of the UF server, "Have fun" let me say that again "HAVE F-U-N!" don't let the ranters get on your nerves, but also take hints from the more experienced players. | 
