Introducing a rescue to my business-need advice

Hey everyone! I'm new to Reddit and looking for advice. I’ve had ferrets for 4.5 years, and last month, I lost one (F4) to lymphoma. Since then, I’ve been spending all my free time with my remaining ferret, Binks (4M). He’s doing okay but plays much less without his sister. Ive been feeling guilty since I couldn’t engage him like another ferret would, I decided to rescue a 1.5 year old lab ferret(F). Their interactions have been neutral so far there has been no aggression, just some initial overwhelm for Binks. I have a few questions: 1. Cage Setup: The rescue owner advised against separating them and suggested they even travel home together. Everything has been fine, but most resources recommend a slow introduction. Since there’s been no negative behavior, should I keep them together? (I sleep in the same room as their cage.) 2. Food Transition: The rescue owner also said I could immediately switch the new ferret to Binks’ food, but my experience suggests a gradual transition is better. Thoughts? 3. Lack of Playfulness: They haven’t had any bad interactions, but they’re also not playing together. When I introduced my original pair, they immediately started play fighting and dooking around. Obviously Binks was much younger then so I know that could have an effect. I’m just worried. will they eventually play together, or should I expect a more neutral relationship? Would love any insights from experienced ferret owners! Thanks!