The underlying hardware of a PSoC1 is quite different from a PSoC3. Additionally the flash and mostly the SRam limitations might be *VERY* pressing.
What I would suggest you is to get hands on a CY8CKIT-059 which is a reasonable replacement for your PSoC3 for a very low price.
There are very significant differences, in tools, Designer PSOC 1, vs Creator for PSOC.
And the components and routability and capability very different.
Converting from PSOC 3 to PSOC 1 a much greater challenge than from 1 to 3.
Take a look at this for a low cost approach to maintaining existing code -
http://www.cypress.com/?rid=108038 CY8CKIT-059 PSOC 5LP
http://www.cypress.com/?rid=77780 CY8CKIT-042 PSOC 4