What liquid was it? If it was water, without any sugary or salty substance (or anything else that might affect the electrical conductivity... so basically anything else except plain water or unsweetened green tea) it's bad look for the computer.
If it was water (or green tea), and it wasn't much, and you immediately unplugged and shut down the computer, let it dry a few days (in full or battery removed or taken apart as much as necessary) before retrying to use it, you might be lucky and see it work just fine. (seen in practice on a few computers. Watering not recommended, but they worked fine...)
If it's any other liquid, replacing more parts may be needed.
Which MacBook Pro is it? 'Unibody' or one of the earlier ones?
The logic board is among the parts that would need changing if it's got any gooey substance in it. If battery got soaked in the substance, that may be safer to change too. And depending on the model of the MBP, the liquid, and where and how much spillage there was, even the casing or the screen - depending if it is possible to simply take it apart and wipe it safely clean.
If what they mean by replacing the laptop that you'd have to fully purchase a new one (as liquid spills aren't covered by warranty), keep your old laptop and don't give it away for free. There are parts in it that are without doubt useful - if not needed for you now, you could sell (ebay, here, craigslist etc) the parts that work and that may work.
Those would include keyboard (all or key by key - as the keys are not typically sold individually, you might consider the key by key option too), optical drive, hard drive (if it works - test using it in target mode with another Mac), casing (if it can't be cleaned... I'm sure it still can be if someone has infinite patience. Or if someone e.g. dropped or bent theirs and want to try to replace the case themself), screen... even the logic board, fans and any other part you could identify. While selling by parts would not get a full price of the laptop back, it is definitely more worth it than giving it away as it is.
