First time flying SAS

[pilot]

Hello all,

Well, my first time flying SAS is rapidly approaching. I'm going to Stockholm for a wedding...flying on UA from LAX-ORD-FRA all in First (miles)...have five hours on the ground in Frankfurt...I guess I'll just hang out in the UA Arrivals lounge until I get bored and check out the LH lounges. I'm a *G (Premier Exec) on United.

A few basic questions...

1.) I'm on a 737-600 from FRA-ARN. What should I expect in economy?
2.) I bought my ticket on Lufthansa so this is a *A/LH/SK code-share flight
3.) I'm on a W fare...is there any chance I could upgrade? How do you do upgrades on SK? Is it even worth it?
4.) Should I check-in online 24 hrs before and snag a good seat, or just wait 'till I get to FRA. Could the lounge agents in either the UA First lounge or LH lounge issue my boarding pass, or do I need to leave the lounge and go get my new BP from the SK desk?

Thanks for your help in advance!
-OxyChaz