I have a MacBook Pro (15-inch, 2.53GHz, Mid 2009) and would like to know if I can replace the battery in it?

Maybe this would give you some idea about your question

For Macs less than 5 years since discontinued:

Apple Mac notebook battery service pricing - United States

Model	Battery pricing
11-inch/13-inch MacBook Air	$129 (excluding taxes)
13-inch MacBook (vintage)	$129 (excluding taxes)
13-inch/15-inch MacBook Pro	$129 (excluding taxes)
17-inch MacBook Pro	$179 (excluding taxes)
12-inch MacBook	$199 (excluding taxes)
13-inch/15-inch MacBook Pro with Retina display	$199 (excluding taxes)

from:

Mac notebooks Service Pricing - Apple Support

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It is moderately difficult,

see > https://www.ifixit.com/Guide/MacBook+Pro+15-Inch+Unibody+Mid+2009+Battery+Replac ement/1712

It can also be done by your local AASP,

click on Service at > https://locate.apple.com/

I found it easy to replace the battery on my MBP. OWC also included the appropriate drivers to perform the task (#00 Phillips and #0 Triwing):

https://eshop.macsales.com/item/NewerTech/BAP15MBU78N/

Ciao.

Apple did not intend those batteries to be user-serviceable. The biggest issue in replacing a battery yourself is that Apple never made/sold batteries for that model as a retail replacement part, creating a sometimes-shady market for third-party batteries. Any such battery that shows up in Apple-branded commercial packaging is an outright counterfeit and should be returned.

Many of these are absolute rubbish at best and could damage your computer. People here have reproted good resutl fomr batteris sold by OtherWorld Computing, and those sold under the "Anker" (spelling?) brand.