Delta site shows no seats available for my flight.

I booked a flight a couple weeks ago through priceline(regular reservation, NOT the name your own price version).
It's 3 segments each way:
MFR to SLC : Delta (operated by Skywest)
SLC to ATL : Delta
ATL to CLT : Delta
then
CLT to BWI : United (operated by US Airways)
BWI to SLC : Delta
SLC to MFR : Delta (operated by Skywest)

I can see my itinerary on Delta.com and I was able to choose seats for all the flights except MFR to SLC and CLT to BWI. When I tried to look at the seat map for CLT to BWI, I got a message saying they couldn't assign seats for that flight. I figured that's normal since it's a United flight.
But when I look at MFR to SLC, it shows me a seat map, it just doesn't show any seats available.
Should I be worried that the flight is overbooked and I may not get a seat?
When I did the online check-in (flight is tomorrow morning), it said it checked me in, but instead of boarding passes, it printed Seat Request cards for the first flight, and it didn't print anything for the second and third flights that day. I tried calling and all they said was that they didn't have any more seats they could assign, but it wouldn't be a problem and I would have a seat assigned at the gate.
Anything to worry about or does this all sound normal?

Thanks

Even if it is overbooked, that doesn't mean you won't get a seat. But without a date and a flight #, I doubt you'll get any additional useful information here.

Based on the above, if you're on the 6:25 am flight there are 3 exit row seats still open.

Thanks for the info. I know even if it was overbooked, I'd be likely to get on. I was just a little nervous about it since I booked through Priceline.
I didn't realize you guys would be able to give me any flight specific info.

Yep, it's the 6:25am. Delta 3871. So how do you know about the 3 exit row seats open?
Do they not normally allow you to pick exit row seats online?

General Skymiles members and/or those without elite status on a partner airline can't preselect "preferred" seats....which include parts of the forward area of coach and most exit rows.

Also, Delta always holds back at least 2 (more on mainline jets) coach seats for gate assignment.....usually the first row of coach.

A.J.