Yes, there are several options.
Taxi: There are always taxis available outside the terminals. A ride to the city center is about 500 SEK (approximately 50 EUR). The ride takes 30-60 minutes depending on the amount of traffic.
Flygbussarna (airport coaches). Has several routes depending on what part of Stockholm you're going to. A single ticket from Arlanda ...
So apparently Qatar Airways has multiple baggage rules. Some routes (to/from US, Canada, Brazil, Argentina) have rules based both on number of pieces and weight, as most other airlines (as far as I know).
In your case (travel between Europe and Asia via Doha), the baggage allowance is only based on the weight you carry. You are allowed 23 kg as checked-in ...
After a bit of research I found that there is something called BagPort which offers "WrapPort" service at Arlanda airport.
It is located in terminal 5 and has a flat price of 70 SEK per bag.
I found a phone number as well; +46-(0)8-797 62 28
BagPort is an umbrella name for a number of services, WrapPort is one but also includes things like baggage ...
If you collect your baggage, you will need to leave the transit zone and check it in for the next flight.
To get out of the transit zone, you would need to go through the passport control, which means you do need a Schengen or Swedish national visa.
As at any other major airport, you can simply walk out of the terminal and catch a taxi. You can only expect the taxi drivers to accept local currency and it may even be difficult to get change for larger bills. In all Scandinavian countries, card payments are much too common for taxi drivers to have plenty of change.
At least in Oslo and Stockholm, you ...
Frequent travellers of Arlanda Airport, as well as airport staff, all know the cheapest beer at Arlanda can be found at McDonald's in Skycity.
One large beer at McDonald's is 65:- (6€).
McDonald's and Skycity can be found in the departures area, before security, between terminal 4 and 5, it's a quick walk from all terminals. If you're in terminal 2 you can ...
Yes on Qatar Airways you can pre-purchase luggage and in fact if you do it online Qatar offer you a discount from doing it over the phone or at the airport.
For their list of rates check out this page on the Qatar website - http://www.qatarairways.com/global/en/excess-baggage-rates.page
If going from Europe to the Far East then it is $13 per kg if paid ...
Check out Stockholm Arlanda's airport map and then check from which terminal airlines operating your flights fly, to see if you need to change terminal and go through the passport control.
Just a reminder: you will need a Schengen visa to go through the passport control. Your residency status in the US is of no importance here.
Flights Sweden-Latvia are effectively domestic, so you will clear immigration in Sweden, not Latvia. And yes, you can enter Schengen anywhere on your D visa.
Have your connecting boarding pass ready to present to the Swedes on request.
There's no transfer desk at ARN, but you can check in for the Turkish flight and print the boarding pass online. Gate staff can also print boarding passes if you're already checked in.
That said, you're probably not getting on the plane to Sweden, because at most departure airports, the staff requires TWOV (sterile transit) trips to be in a single booking, ...