I have a Compaq C502US Laptop with Windows Vista Home.

It came with 512 of ram.

How difficult is it to add another 512 of ram?

I've never even seen the inside of this laptop so if this is a fairly easy task, please provide as much detail as possible.

If this is too difficult for a beginner, what would a good price range be to have it done?

Thank You!

I would recommend 1gig of ram instead of another 512 mb if you want smoother gameplay if that's what you use it for but if its just for general computing the I would go for the 512mb ram if price is also issue then stick to 512mb ram if not then I recomment just getting 1 gb ram the youl have 1 1/2 ram I have a gaming computer and I have 4gig ram so that's overkill so what I'm saying I would go for the 1 gig ram

Check your laptop empty slot for memory, if have then buy 512Mb as it is cheaper but 1G if u want faster. U can't have more than 3 Gb of ram as u're not using ultimate version of Vista nor business.

Bear in mind that a 32 bit OS such as XP or Vista CANNOT access anymore than 4 gig TOTAL RAM.
There can also be BIOS issues as well.
Total RAM includes all installed RAM and Graphics card memory as well.

So if, like me, you have a 512Mb Graphics card and add 4Gb RAM the system will only be able to access/use 3.25 Gb of the installed RAM.