Actually, it is pretty easy. Eat enough protein to sustain your LBM (roughly 1g per lb of current body weight), workout consistently with heavy enough weights to recruit active muscle fibers (both slow and fast twitch by varying reps, sets and weight), eat several smaller meals throughout the day so that muscles are constantly being supplied with the amino acids they require and do not have to resort to eating your hard earned muscle, and keep carbs at a level that allows you to do all this.

Dolly, it is very likely that you will build on your 105 lbs of lean mass. It is also possible that you can lose a few lbs of it - but if you are new to weight lifting it is less likely than if you had been doing resistance work for years. Newbies to weight lifting can experience dramatic losses in body fat and gains in muscle mass at the same time - this doesn't last though - so enjoy it now

Nat