The hard drive in my MkII is going bad. Sometimes it won't spin up, etc.

When I'm looking for a replacement, is there anything that I should get or will any laptop drive work fine?

Some people have had to manually build hard drives of 80 gb or greater on mk II units. Pretty much any drive should work just fine some sites have 80 gb units for around ~ 115 usd .

Check the ide cable and header to look for damage. Be careful taking the connector on and off a drive. If you can find some of those little red washers use them inbetween the screw and drive mounting. Dont overtighten anything.

The quick answer is that any laptop hard drive today will work. For reference, though, it should be IDE and rotation speed really will not help you much, so slower (i.e., cheaper) is actually better and runs cooler. Choose a good manufacturer - Fujitsu and Hitachi seem popular, but everyone has a favorite. In a MarkII with 12MB of RAM, you may have trouble building larger drives (>80GB) because the builder software does not activate swap first. Use the manual drive partitioning and formatting guides if possible. Have fun!