The number one hit for ‘replacing baseboard heating covers’ is a This Old House Episode that looks pretty daunting.  My son and I just knocked this out in less than an hour.  Here’s what we did:

1. Measure
   1. We had 3 baseboard heeaters.
   2. 1 was 5 feet
   3. 1 was 10 feet = 2 * 5 feet.
   4. 1 was 12 feet = 2 * 6 feet.
2. Order from Baseboarders.com.  Our order arrived in less than 2 days.
3. Remove the ends – some were already done from measuring in Step 1.  Be safe!
4. Vacuum, clean and de-dust.  Be safe!
5. Install new covers.  End caps on first.  Connectors on last.