I have rheumatoid arthritis and see my rheumatologist every 3 months. When I get my monthly labwork done, it is at my local hospital lab, but many times the labs can be done at the office. All my labs are usually bloodwork and no fasting is required. I doubt that you'd have to stay overnight. If they suspect that you have RA they will be looking at your rheumatoid factor, blood count, and sed rate.
Depending on the reason for the referral, the Dr. will ask you many questions about your history and your symptoms. He/she will look at your joints and ask you to move them. In RA the joints are affected on both sides (both wrists, hands etc), with OA (osteoarthritis) it is not usually the case. There are MANY different kinds of arthritis and joint related conditions, such as lupus, fibromyalgia, and more. My dr is wonderful!! I was diagnosed 5 years ago, and am doing great due to the care she gives and the combination of 4-5 rx meds I take. 5 years ago I was 38 and walked like a 90 year old, couldn't tie my 4 year old's shoes, and could barely move for an hour after waking. I couldn't even hold a toothbrush. Now you'd barely see anything wrong and I am living pretty normally.
I could go on and on, so if you need any info at all, or just want to talk to someone who has RA just PM me.