dtech

I believe the bike maybe 15 yrs old or so, it is aluminum frame, I have ridden it extensively (200 + miles weekly) , replacing rear cassettes multiple times, rear derailluer and the crank bearings and chain rings. Now the 8 speed trigger shifter is giving it up - the spring is weak (I would clean and lube the shifters periodicaly) , the large chain ring also needs replacing, I have the following questions :
- how stressed might the aluminum frame be at the point, I go some 190 lbs.
- can I convert the 8 speed to 10 speed by replacing chain, chain ring, shifter and rear cassette, and would the rear derailluer also need replacing ?
- or should I just keep it a 8 speed.
I do my own work and when needed have replaced the original shimano ultegra components with dura ace

advice/opinions are welcome, I tend to ride my bikes until there isn't much left in them, had a viscount aerospace with the old thin tubes that I rode for many years and miles, but if it's wise not to put $$ into the Fuji and look for a new bike I'm listening.