New drive in ancient VGN-T350?

My wife has a VGN-T350P and would like to improve it's boot up times.  For everything else the machine's performance has been adequate.  We've got all the accessories for it so upgrading to a different machine would cost quite a lot than just the machine (docks at home & office, chargers, spare battery, bag, sleeve, etc). 

I'm wondering about slapping an SSD into it to replace the drive that's in there now.  I just haven't been able to nail down what sort of drive or adapter cables I'd need to use to make it work.  I realize it's a 1.8" drive, but what sort of interface?  And does anyone make an SSD that'd plug right into place?  Or do I need some form of adapters.

I'm not quite prepared to go the route of ripping out the optical drive and using a 2.5 SSD.  She does use the DVD now and then so ripping it out would be a problem.

So what're my options?  Thanks!

There aren't any faster RPM drives.  4200 is it for the 1.8" form factor.  The machine already has it's max 1GB of RAM.  All unnecessary services and software are already disabled.

Is there some other reason for not going with an SSD?   Unless there's a real issue with NO performance gains then it'd be just a money issue.  I'm fine with 'wasting' the money on upgrading this machine if is actually improved performance.  But if someone can show me that an SSD will perform exactly the same as the existing HD then that would nix the upgrade.

No chance?  I'd argue against that.  But enough of an improvement to be worthwhile, well, that depends on your perspective on worth.  I think what I'm going to do is test it first with a regular 2.5" SSD and an adapter.  If that doesn't provide at least a 33% boot time improvement then I'll abandon the idea.  Yes, it's probably not 'worth' the money to do this except for the fact that my wife likes the machine and has all the accessories.  Trying to overcome THAT notion is a lot harder than wasting money, follow me?