If you can afford it, i would get both. I say dont get elite reps because you will hit both the repair cap and SD cap with +12s or 11s, maybe not as fast but you will reach it. I say get the elite engis because you will get the speedcap faster and im not sure if theres a limit on overheat time but if there isnt, more is better and they will get you more. However, both sides have valid points and if you get both, you will reach all the caps related to the sailors faster, which is never a bad thing. If you can only get one set, go with the engis because of the extra OH time; you will hit the repair and SD caps either way eventually. However it is also up to you so you might want to take into consideration what cap you want faster.

I see that I made a typo up above when I asked about "elite" when I actually meant should I boost my supports as premium sailors.

I'll take that as a yes. 

At this point, boost all your crew. Then get at least 100 vets on everything, starting with gunners, then engineers, then repairs. Your BO only if your gunlines are still shorter than your range. Otherwise leave it. Your scout is your personal opinion/money avalible. Since scouts were change to using their own ability. +12 Aircraft scout with 250 vets can rape fighters in 1 on 1-3 situations.

If your short on cash, vet first, Boost just "boost" the base ability of your sailors. Vets multiply that ability. Vets > Boost. but if you can afford it, get both asap.

Boosting alone should get you into the 550ish SD Range. Vets will get you into the 700-750 range. You won't hit 900 SD until your above level 95. Getting all your supports near the same level would help. Your crew minus your BO should all be within 5 levels of eachother at all times.

Also its time to return the restorer. Don't get used to the restore boost they give. They become wasted space above lvl 85 as with boost and vets, you can easily get into the 700-800 range with reps and engineers. Cap is 900 SD.

If you plan on continuing up to Nebraska, get another rep and engy, or 2 engineers. You'll want 10 total reps and engys. I personally use 5/5 since my main crew is only 100-110 vets. But if you can get 200 vets on your engies and reps, then 4/6 is the way to go.

I suggest getting another BO, 1 rep and at least 1, if not 2 engineers (maybe some reload gunners for AA/HH?). (As having options @ 120 is way more fun than stuck with 1 crew layout), This will also allow you to catch up your lower level rep. Your current North Hampton line BO, bring it up the Tenny line, bring your 3rd new BO up the penny line. Having played the Colorado, the tenny is pretty simular (Less ammo) and the Penny is one fun ship. After these I suggest trying out your Colorado again. Its one beast ship with 900 SD, speed capped @ 44 (or 42 if your crew is too heavy) and havin a ton of OH time. You'll really change your opinion.

Once your 2 Nor Cal line BOs are up to, well, the North Carolina, Switch back and forth between the 2 BB3s. The Iowa sorta plays like the Sodak with the North Carolina's Hang time. Get use to both. Once you get 850-900 SD, get your highest level BO and grind up the Iowa, Montana and Nebraska, Your gunners and crew will be 10-20 levels above the ship, allowing you to abuse their advantages without the extra limitations cause by the lower level crew. You'll love USN with 900 SD, 200+ DP/sec rep and OH capped.

 

If you want some referrence on how trustable this is, I have every USN Ship, including Premium and Event ships, also the APA, I've also used all the US Rentals but the Rental Iowa and Rental Montana. (Unless you count the rental Iowa on the old test server years ago but one mission doesn't count in my eyes.)

I think I said this already but you should be able to fairly easily get to 70 vets or so during an event.  That doesn't mean 10 tries to get 7 conversions (although I have done that a few times), you should be able to do it with 120-150 experts.  After that use the +1 vet items and set your sailors to X9.  From there, you can use the +10 items to get to 109 vets.  At that point you cannot use vet items.

Remember, compound conversion during events by getting the short(or month) premium.  It does make a difference and during that time, you might want to AA as the expert gain is also increased and you'll find it fairly easy to refill your sailors.