Maintenance on a heating unit, water heater, or both

I hear this stuff is important, but if you know nothing about it (like me) then you may want to call the experts in for help! At least you won't have to pay a lot to do it. Sal's Heating and Cooling is offering:

$39 for an inspection and a cleaning for one heating unit (an $82.50 value)
$39 for an inspection and a tune up for one water heater (an $82.50 value)
$75 for an inspection package (a $165 total value) that includes:
     An inspection and a cleaning for one heating unit (an $82.50 value)
     An inspection and a tune up for one water heater (an $82.50 value)

*If you haven't signed up for Groupon yet, I'd appreciate it if you used my reference link. It helps me out :-) Thanks!