Our facility does 10-20 of these daily... but it's different if your the patient and I recognize that! all the above advise is excellent. You'll be taken to a cath lab or EPS "suite", the doc will enter your groin with a 6 or 7 french cath, after numbing the site with lidocaine.
Are you nervous? heck yes, that's why you have an RN specifically assigned to you through the whole proceedure, who's job is to keep you comfortable. We use fentanyl and versed through an IV, conscious sedation. You won't be "knocked out", but few patients remember the proceedure, due to the versed, most if not all say it was not as bad as they expected.
Now assuming the doc, can ablate the irritable spots via the right groin, you're all set. 4 hr.s most bedrest, some facilities use a 10 lb. sandbag to the groin, others use an occlusive seal. If they ned to enter the left groin which is rare, you'll have two entry sites, and naturally, the docs, and staff are a bit more cautious with letting you sit at a 90 degree angle and walking around until they are sure that stable clots have formed in your femoral veins, and it is safe.
Now Worst case senario, the irritable focci is in you SA or AV node, and they must ablate there.... you'll need a pacer. This is very rare, but very real. You'll have 6 weeks of activity restrictions, not lifting more than 10 lbs, not lifting the affected arm higher than your shoulder, (the wires need time to adhere and heal to the myocardium, lifting up pulls at their insertion point).
But again, you are the patient, you can always refuse a pacer, but this will lead into a life of meds not only for rate controll, but anticoagulation for the obvious, as well as weekly and monthly lab work to monitor, not worth it in my book, just fix it!
Hope this helps, this is one of my areas of expertise, feel free to PM me at any time