I too recently bought a used 2002 Tiffin Allegro Bay 35DA w/8.1L and Allison. I've only taken a couple small trips but like it so far. So far I've replaced or fixed the following.
2 front tires
Dometic fridge rooftop cover
Resoldered loose connections on circuit board for rear BR slide
Replaced 2 house batteries
Repaired engine A/C - leak checked, pulled vacuum and recharged
Rewired power window on drivers exit door
Oil and filter change
Made new metal panel to replace broken plastic 12V panel by entrance door
Rewired 12V panel by entrance door
Rewired electric steps
Cleaned rust off propane tank and repainted
Polished plastic headlamp lenses that were fogged over
Replaced BR TV
Replaced broken rooftop antenna W/sensar IV
Resealed rooftop seams w/ self leveling lap sealant
Serviced generator
Replaced RF ABS sensor
Replaced gas cap
Approx. cost doing my own work $1500.
Still to do
Replace hyd. jacks (all 4) only one retracts. Already replaced all 8 return springs and through troubleshooting determined jacks are either bent or bad internal seals
Replace awning
Replace brake pads - they passed inspection but was told they'll need replacing by next year