Was Told Seroma After Liposuction Will Take a Year to Reabsorbing, Should it be Aspirated?

Yes you could but if clotted blood than very hard to aspirate. I recommend lymphatic massage and external ultrasound therapy. 

This sounds like normal post op swelling and bruising at 1 week.  If it is entraped blood it can not be aspirated.  I would be patient ;wear your garment and elevate your legs when possible.

Localized swelling following liposuction usually means that you have a seroma (a collection of serum) or a hematoma (a collection of blood).  If a discreet fluid collection can be felt, I will usually aspirate the area and follow the patient closely (at least 3 days/week).  If the swelling is generalized and, in your case, only one week after the surgery, compression garments, elevation and a low salt diet should help as the swelling subsides over time.  If this is a hematoma as you have been told, I would aspirate the blood if possible to minimize the development of scar tissue and decrease the risk of infection.  If the blood has already clotted, then time is your best option and indeed it can take up to one year for this to resolve.