Looking for some tips to get these awards faster? Well, you came to the right post. (I hope so, anyway)
As with my Assault guide, let's start with what you should equip. The UMP-45 is your all-around submachine gun, being only slightly better than the SCAR-L because of its nice shot spread (or more specifically, lack of spread). Its 25 count magazine puts it at a slight disadvantage, although not quite as much as the 20-count of the 9A-91 (laughable gun in my view). SO, you might be thinking that it doesn't need the Marksman SMG Training for increased accuracy. Well, you probably are, but if you take a 4x scope in conjunction with it, you have a nice and accurate medium-range weapon. I personally think a red dot sight and magnum ammo would be your best bet, but it's up to you.
Onto the awards: Reach a killstreak of 5 with the UMPP-45 SA. This one will probably be more tricky for some than the M16A2 killstreak. The SMG's primary role is personal defense after all, so unless you've got some balls, I recommend against charging the front lines. An ideal position would be hanging around the M-COM stations as a Defender, so you can take out hostiles who might be focusing more of their attention on arming charges. Also, you might squander a lot of ammo trying to kill opponents, and you can't always count on having awesome Assault teammates who give you ammo. Thus, the equipping the Ammo Hip Bandolier in Spec slot 1 might be wise. This sacrifices your scope and forces to use iron sights, however.
Next: 8 kills in a round with the UMP-45 SA. A bit challenging, but not too big of a feat. Hang around M-COM buildings and natural choke points on the map. If you find any idle/distracted players that you sneak up on, forego the obvious knife kill and go for another UMP kill.
Final: 100 kills total with the UMP-45 SA. This one is probably gonna take a few sessions (by sessions, I mean nights of playing multiple rounds) of playing as Engineer with the UMP-45 SA. Look for bonus kills whenever possible (such as the knife situation as explained up above), but don't ignore your rocket launcher completely. Definitely take out any vehicles you can; it's points, and it lets you be a credit to the team. In fact, you might even scare dumb chuckleheads to abandon their tank after 1-2 rockets, from which you can UMP-45 their cowardly asses. Don't ignore friendly tanks, either; repairing them really helps out... but don't feel obligated to be a dedicated repairman the whole match. You've got your own stuff to do.
All in all I'd say that the UMP-45 SA achievement might be the second hardest to obtain for the average Bad Company 2 player, but by no means mind-blowingly difficult.