A guide is a salesperson; you would not need to work with them unless you wish to purchase additional points direct from Disney. For reservations, you'd call Member Services, for financial questions/issues, you'd call Member Accounting. For problems with your membership, call Member Satisfaction.
One will be assigned to you whether you purchase direct or resale. They generally don't contact you unless you contact them. I haven't talked to mine since the day I bought, 12 years ago.