Install an SSD into the optical superdrive slot on a MacBook Pro | OSXDaily
MacBook and MacBook Pro (Non-Retina) SSD Upgrade Bundle - iFixit Store
OWC SSD Upgrade Kits For MacBook Pro (2008 - 2009)
MacBook Pro Early 2008 Upgrade SSD
OWC SSD Upgrade Kits For MacBook Pro (2008 - 2009)
MacBook Pro 15" Unibody Late 2008 and Early 2009 Hard Drive Replacement - iFixit Repair Guide
MacBook Pro Retina: Upgrading to SSD (Howto)
How-To: Upgrade the SSD in your MacBook Air or Retina MacBook Pro, boosting size & speed - 9to5Mac
Installing MacBook Pro 15" Unibody Late 2008 and Early 2009 Dual Hard Drive - iFixit Repair Guide
OWC SSD
Even after 12 years, my late 2008 MacBook Pro hasn't given up. Upgraded it to 8GB of ram, added an SSD, and patched it with MacOS Catalina. Still use it everyday. :
SSD for my Late 2008 MacBook Pro? | MacRumors Forums
2008 MacBook Review: Better than a modern MacBook in many ways
MacBook Pro Early 2008 Upgrade SSD
How to add a fast new SSD to your old Mac or MacBook for only $150 - 9to5Mac
MacBook Pro Running Slow? You Need A Solid State Drive - DJ TechTools