We are planning on purchasing our first tt this Friday. It is a Jayco Sport 199 & it only has a single sink in the kitchen & no lavatory. How difficult would it be for us to intall a double sink ourselves. We are not skilled plumbers.! Also, I would like to replace the black water holding tank. Does this require welding or is it attached with bolts. I don't like the idea of empyting a tank someone else has used. Thanks for any help. I usually don't get any reponse to my questions but I would really appreciate any help before I commit to buying this trailer.