I bought a Waterford Schwinn Paramount recently. It's gorgeous, but it's geared too high. I want to make my life a bit easier on the hills, while keeping the group as intact as possible.

Here's what's on there now:

• Shimano 105 8-speed
• 53/42 crankset
• 12-23 cassette

Here are my options/questions:

1. Swap 42t for 39t: Is there anything I have to look out for other than BCD? Will a 9-speed chainring work without issue?
2. Swap rear cassette for 12-28: Can I purchase a modern Shimano-compatible, 8-speed, 12-28 cassette and put it on a late 80's Shimano 105 rear hub and expect it to work? If not, what do I have to look for... smaller max cog size, different spline standards?
3. Swap crankset: Hypothetically, what if I just say 'screw it' and throw on an Ultegra Compact crankset? Would that work with the rest of the group - i.e. front derailleur - without swapping out other parts?

Thanks in advance for any info you can offer.

PS - yes, I plan on rectifying the saddle, stem, handlebar and pedal situation.