Need to lose weight and bulk up!?

I'm currently about 20 lbs overweight and it's been affecting my posture, and causing more pain on my knees and feet. I've always been around 155-160, but this past year I've been somewhat sedentary and have put on too much weight, and I'm now at 180-185. I need to lose at least 15 pounds but I also want to put on muscle. I want to do this as quickly as possible but safely too. I have access to some old-school Nautilus-style weight equipment and stationary bicycles too. Jogging and running are not really an option for me due to ankle, feet and knee issues. I have a sauna in my apartment clubhouse too. I cant afford to go on some fancy all health-food diet, but i can cut back on carbs, etc. Any other dietary advice would help too. p.s. I'm 45 years old and in otherwise reasonably good health.