What's the easiest/cheapest way to replace my battery? 2009 MBP I have a 2009 MacBook Pro (5,5);  also identified as the A1278 (EMC 2326). I can spend about $150 either taking it to the Apple Store and having them replace it or buying all the stuff from iFixit.com and doing it myself.

Is there any cheaper/easier way of doing this? Would an independent Apple repair shop be any less expensive? Are there any reliable third-party batteries? I have some crucial RAM and would be comfortable using a Crucial SSD (if I didn't already have a stock one), I'm not particular to an Apple-sourced battery if there's another one that's equally reliable.
Having recently done this for a colleague, I can answer in the affirmative that there are excellent 3rd party battery suppliers for this particular model MacBook Pro and they are quite easy to replace.

I used the Lizone battery mainly for it's high ratings on Amazon and the fact it came with an 18 month warranty (better than Apple's 1 year warranty).

Replacement was super easy.  There is a guide on ifixit.com but I didn't really need it.  I just removed the back cover, removed the screws holding the battery and used a plastic pry tool to gently pry the battery loose from the adhesive.  Installation was simply the reverse procedure.

Since I had everything opened, I maxed out the memory with 8GB of RAM and added a Samsung EVO SSD.  While I am partial to Samsung, PNY and Crucial are also very good brands.  Basically, any 2.5" SSD will work in this MacBook so pick one that you like the best.

It's important to note that the SATA interface of this particular MBP is SATA II (3GB /s transfer rate).  If you can get a SATA II drive, it will work just fine.  SATA III is backwards compatible, but you won't see increased speeds above the 3GB /s transfer rate.